U.S. patent number 10,625,196 [Application Number 15/168,709] was granted by the patent office on 2020-04-21 for coalescing filter media.
This patent grant is currently assigned to Hollingsworth & Vose Company. The grantee listed for this patent is Hollingsworth & Vose Company. Invention is credited to Jens-Peter Boesner.
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United States Patent |
10,625,196 |
Boesner |
April 21, 2020 |
Coalescing filter media
Abstract
Filter media, filter elements, and methods for filtering an gas
stream are described herein. In some embodiments, the filter media
may comprise a fiber web comprising a plurality of fibers and
having a particular oil repellency level. For instance, in certain
embodiments, the surface chemistry of the fiber web may be tailored
to impart a particular surface energy density that matches the
surface energy density of the fluid (e.g., an oil, a lubricant,
and/or a cooling agent) being removed from the gas stream. In some
embodiments, the fiber web may be wrapped around a core. For
example, the fiber web may be wrapped around the core such that it
forms two or more layers around the core. In some cases, the fiber
web may be perforated. In certain embodiments, an gas stream
comprising a fluid (e.g., an oil, a lubricant, and/or a cooling
agent) may be passed through the fiber web, filter media, and/or
filter element such that at least a portion of the fluid coalesces
on the fiber web. Fiber webs, filter media, and/or filter elements
as described herein may be particularly well-suited for
applications that involve filtering gas streams containing oil,
lubricants, and/or cooling agents (e.g., gas streams generated by a
compressor) though the media may also be used in other
applications. Advantageously, the fiber webs, filter media, and/or
filter elements described herein may significantly reduce or
prevent fouling of the filter caused by oil or other liquids.
Inventors: |
Boesner; Jens-Peter (Hatzfeld,
DE) |
Applicant: |
Name |
City |
State |
Country |
Type |
Hollingsworth & Vose Company |
East Walpole |
MA |
US |
|
|
Assignee: |
Hollingsworth & Vose
Company (East Walpole, MA)
|
Family
ID: |
60421103 |
Appl.
No.: |
15/168,709 |
Filed: |
May 31, 2016 |
Prior Publication Data
|
|
|
|
Document
Identifier |
Publication Date |
|
US 20170341006 A1 |
Nov 30, 2017 |
|
Current U.S.
Class: |
1/1 |
Current CPC
Class: |
B01D
46/528 (20130101); B01D 46/0001 (20130101); B01D
39/2017 (20130101); B01D 39/1623 (20130101); B01D
39/18 (20130101); B01D 46/521 (20130101); B01D
2239/1233 (20130101); B01D 2239/1258 (20130101); B01D
2275/105 (20130101); B01D 2239/0654 (20130101); B01D
2239/1291 (20130101); B01D 2239/0421 (20130101); B01D
2279/30 (20130101); B01D 2239/0695 (20130101); B01D
2239/08 (20130101); B01D 46/003 (20130101); B01D
2239/0478 (20130101) |
Current International
Class: |
B01D
39/18 (20060101); B01D 46/00 (20060101); B01D
39/16 (20060101); B01D 39/20 (20060101); B01D
46/52 (20060101) |
References Cited
[Referenced By]
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Other References
International Search Report and Written Opinion for PCT/US17/35226
dated Aug. 24, 2017. cited by applicant.
|
Primary Examiner: Holecek; Cabrena
Attorney, Agent or Firm: Wolf, Greenfield & Sacks,
P.C.
Claims
What is claimed is:
1. A method for filtering an oil, lubricant, and/or cooling agent
from a gas stream, the method comprising: passing the gas stream
including the oil, lubricant, and/or cooling agent through a filter
element, wherein the filter element comprises a fiber web wrapped
around a core such that at least two layers of the fiber web are
formed, the fiber web comprising: a plurality of fibers having an
average fiber diameter of at least 0.01 microns and less than or
equal to 50 microns; a basis weight of at least 1 g/m.sup.2 and
less than or equal to 270 g/m.sup.2; and a thickness of at least
0.01 mm and less than or equal to 5.0 mm, wherein the fiber web has
an oil repellency level of between 4 and 6; wherein the fiber web
has an oil carry over of less than 20%, and wherein the oil,
lubricant, and/or cooling agent has a surface tension of between 22
mN/m and 33 mN/m measured at 23.degree. C. and 50% RH.
2. The method of claim 1, wherein the gas stream is generated by a
compressor, natural gas production equipment, a distillation
column, an evaporator, a thermal oil ventilator, a crankcase
ventilator, a combustion engine, and/or an exhaust conduit.
3. The method of claim 1, wherein the fiber web comprises binder
fibers, wherein a weight percentage of binder fibers present in the
fiber web is at least about 0 wt % and less than or equal to about
10 wt %.
4. The method of claim 1, wherein the fiber web comprises glass
fibers, wherein the weight percentage of glass fibers present in
the fiber web is greater than or equal to about 0% and less than or
equal to about 99% by weight of the total fibers in the fiber
web.
5. The method of claim 1, wherein the fiber web comprises synthetic
fibers, wherein the weight percentage of synthetic fibers present
in the fiber web is greater than or equal to about 1% and less than
or equal to about 100% by weight of the total fibers in the fiber
web.
6. The method of claim 1, wherein the fiber web comprises cellulose
fibers, wherein the weight percentage of cellulose fibers present
in the fiber web is greater than or equal to about 1% and less than
or equal to about 100% by weight of the total fibers in the fiber
web.
7. The method of claim 1, wherein the fiber web has at least one
modified surface.
8. The method of claim 1, wherein the fiber web has an initial
efficiency of greater than or equal to about 1% and less than or
equal to about 99.99%.
9. The method of claim 1, wherein at least one surface of the fiber
web is coated with a coating.
10. The method of claim 9, wherein the coating comprises a
fluorinated polymer.
Description
FIELD OF INVENTION
The present embodiments relate generally to coalescing filter
media, and specifically, to coalescing filter media having enhanced
oil repellency levels and/or performance characteristics, and
related methods.
BACKGROUND
Filter elements can be used to remove contamination in a variety of
applications. Such elements can include a filter media which may be
formed of a web of fibers. The fiber web provides a porous
structure that permits fluid (e.g., gas, liquid) to flow through
the media. Contaminant particles (e.g., dust particles, soot
particles) contained within the fluid may be trapped on or in the
fiber web. Depending on the application, the filter media may be
designed to have different performance characteristics.
Although many types of filter media for filtering oil from gas
streams exist, improvements in the physical and/or performance
characteristics of the filter media (e.g., strength, air
resistance, efficiency, and high dust holding capacity) would be
beneficial.
SUMMARY OF THE INVENTION
Coalescing filter media and related methods are generally provided.
The subject matter of this application involves, in some cases,
interrelated products, alternative solutions to a particular
problem, and/or a plurality of different uses of structures and
compositions.
In one aspect, methods for filtering an oil, lubricant, and/or
cooling agent from a gas stream are provided. In some embodiments,
the method comprises passing the gas stream including the oil,
lubricant, and/or cooling agent through a filter element, wherein
the filter element comprises a fiber web wrapped around a core such
that at least two layers of the fiber web are formed, the fiber web
comprising a plurality of fibers having an average fiber diameter
of at least 0.01 microns and less than or equal to 50 microns, a
basis weight of at least 1 g/m.sup.2 and less than or equal to 270
g/m.sup.2, and, a thickness of at least 0.01 mm and less than or
equal to 5.0 mm, wherein the fiber web has an oil repellency level
of between 4 and 6, wherein the fiber web has an oil carry over of
less than 20%, and wherein the oil, lubricant, and/or cooling agent
has a surface tension of between 22 mN/m and 33 mN/m measured at
23.degree. C. and 50% RH.
In some embodiments, the method comprises passing the gas stream
including the oil, lubricant, and/or cooling agent through a fiber
web, wherein the fiber web comprises a plurality of fibers having
an average fiber diameter of at least 0.01 microns and less than or
equal to 50 microns, a basis weight of at least 1 g/m.sup.2 and
less than or equal to 270 g/m.sup.2, and a thickness of at least
0.01mm and less than or equal to 5.0 mm, wherein the fiber web has
an oil repellency level of between 4 or greater and 6 or less, and
wherein the fiber web comprises a plurality of perforations having
an average cross-sectional dimension of at least about 1 mm.
In another aspect, filter elements are provided. In some
embodiments, the filter element comprises a core and a fiber web
wrapped around the core such that at least two layers of the fiber
web are formed, wherein the fiber web comprises a plurality of
fibers having an average fiber diameter of at least 0.01 microns
and less than or equal to 50 microns, a basis weight of at least 1
g/m.sup.2 and less than or equal to 270 g/m.sup.2, and a thickness
of at least 0.01mm and less than or equal to 5.0 mm, wherein the
fiber web has an oil repellency level of between 4 or greater and 6
or less, and wherein the fiber web has an oil carry over of less
than 20%.
In yet another aspect, filter media are provided. In some
embodiments, the filter media comprises a fiber web, wherein the
fiber web comprises a plurality of fibers having an average fiber
diameter of at least 0.01 microns and less than or equal to 50
microns, a basis weight of at least 1 g/m.sup.2 and less than or
equal to 270 g/m.sup.2, and a thickness of at least 0.01mm and less
than or equal to 5.0 mm, wherein the fiber web has an oil
repellency level of between 4 or greater and 6 or less, and wherein
the fiber web comprises a plurality of perforations having an
average cross-sectional dimension of at least about 1 mm.
Other advantages and novel features of the present invention will
become apparent from the following detailed description of various
non-limiting embodiments of the invention when considered in
conjunction with the accompanying figures. In cases where the
present specification and a document incorporated by reference
include conflicting and/or inconsistent disclosure, the present
specification shall control. If two or more documents incorporated
by reference include conflicting and/or inconsistent disclosure
with respect to each other, then the document having the later
effective date shall control.
BRIEF DESCRIPTION OF THE DRAWINGS
Non-limiting embodiments of the present invention will be described
by way of example with reference to the accompanying figures, which
are schematic and are not intended to be drawn to scale. In the
figures, each identical or nearly identical component illustrated
is typically represented by a single numeral. For purposes of
clarity, not every component is labeled in every figure, nor is
every component of each embodiment of the invention shown where
illustration is not necessary to allow those of ordinary skill in
the art to understand the invention. In the figures:
FIG. 1 is a schematic diagram showing a cross-section of a filter
media according to one set of embodiments;
FIG. 2 is a schematic diagram showing a perspective view
cross-section of a filter according to one set of embodiments;
FIG. 3 is a schematic diagram showing a cross-section of a filter
according to one set of embodiments;
FIG. 4 is a schematic diagram showing a cross-section of a filter
media according to one set of embodiments;
FIG. 5 is a schematic diagram showing a perspective view
cross-section of a filter according to one set of embodiments;
and
FIG. 6 is a schematic diagram showing a perspective view
cross-section of a filter according to one set of embodiments.
DETAILED DESCRIPTION
Filter media, filter elements, and methods for filtering a gas
stream (e.g., air) are described herein. In some embodiments, the
filter media may comprise a fiber web comprising a plurality of
fibers and having a particular oil repellency level. For instance,
in certain embodiments, the surface chemistry of the fiber web may
be tailored to impart a particular surface energy density that
matches the surface energy density of the fluid (e.g., an oil, a
lubricant, and/or a cooling agent) being removed from the gas
stream. In some embodiments, the fiber web may be wrapped around a
core (e.g., an inner core). For example, the fiber web may be
wrapped around the core such that it forms two or more layers
around the core. In some cases, the fiber web may be perforated. In
certain embodiments, an gas stream comprising a fluid (e.g., an
oil, a lubricant, and/or a cooling agent) may be passed through the
fiber web, filter media, and/or filter element such that at least a
portion of the fluid coalesces on the fiber web. Fiber webs, filter
media, and/or filter elements as described herein may be
particularly well-suited for applications that involve filtering
gas streams containing oil, lubricants, and/or cooling agents
(e.g., gas streams generated by a compressor) though the media may
also be used in other applications. Advantageously, the fiber webs,
filter media, and/or filter elements described herein may
significantly reduce or prevent fouling of the filter caused by oil
or other liquids and/or increase the coalescence and/or continuous
removal of the oil or other liquids.
An example of a filter element including a fiber web and a core) is
shown in FIG. 1. In some embodiments, the fiber web may be adjacent
(e.g., directly adjacent) the core. As shown illustratively in FIG.
1, a filter element 100, shown in cross section, may include a
fiber web 110 comprising a plurality of fibers and a core 120
directly adjacent fiber web 110. In some embodiments, the fiber web
may be wrapped around the core. For example, as shown
illustratively in FIG. 2, filter element 102 comprises fiber web
110 wrapped around core 120 (e.g., a non-fibrous component, such as
a core). In certain embodiments, the fiber web is wrapped around
the core such that the fiber web substantially covers at least a
portion of the surface of the core along a circumference of the
core. In some embodiments, the fiber web is wrapped two or more
times around the core. For example, in certain embodiments, the
filter element comprises at least two layers of the fiber web
wrapped around the core. The core may comprise, for example, a wire
mesh or a perforated sheet, and may be formed of metal or plastic
in some embodiments. Additional examples of cores are described in
more detail below.
As used herein, when a layer is referred to as being "adjacent"
another layer, it can be directly adjacent to the layer, or an
intervening layer also may be present. A layer that is "directly
adjacent" another layer means that no intervening layer is
present.
As shown illustratively in FIG. 3, filter element 106 comprises
fiber web 110 wrapped around core 120 such that filter element 106
comprises two layers of fiber web 110. In some embodiments, the
fiber web is wrapped continuously around the core. That is to say,
in some such embodiments, a single fiber web may be wrapped around
the core such that at least one continuous layer is formed. In some
embodiments, the single fiber web may be wrapped around the core
such that at least two layers of the single fiber web are formed.
In some embodiments, the filter element may comprise at least 1, at
least 2, at least 3, at least 4, at least 5, at least 7, at least
9, at least 10, at least 11, at least 13, at least 15, at least 17,
or at least 19 layers of the single fiber web wrapped around the
core. In certain embodiments, the filter element comprises less
than or equal to 20, less than or equal to 19, less than or equal
to 17, less than or equal to 15, less than or equal to 13, less
than or equal to 12, less than or equal to 11, less than or equal
to 10, less than or equal to 9, less than or equal to 7, less than
or equal to 5, less than or equal to 4, less than or equal to 3, or
less than or equal to 2 layers of the single fiber web wrapped
around the core. Combinations of the above-referenced ranges are
also possible (e.g., at least 1 layer and less than or equal to 20
layers, at least 2 layers and less than or equal to 13 layers, at
least 2 layers and less than or equal to 4 layers, at least 5
layers and less than or equal to 10 layers). Other ranges are also
possible.
The fiber web may have any suitable configuration with respect to
the core. For instance, it should be understood that the fiber web
need not wrapped around a core in all embodiments. For example, in
certain embodiments, one or more layers comprising the fiber web
may be disposed within a core (e.g., an outer core).
Configurations of the fiber web may also vary. For example, in some
embodiments, one or more layers comprising the fiber web may be
directly adjacent one or more support layers. The support layer may
comprising a mesh and/or a plurality of fibers such as synthetic
fibers, cellulose fibers, and/or glass fibers as described in more
detail below. In some embodiments, a filter element or filter media
comprising the fiber web may comprise two or more support layers.
The support layer(s) may be positioned upstream and/or downstream
of the fiber web layer(s). In some embodiments, the fiber web
layer(s) along with the support layer(s), if present, may be
wrapped around a core in a filter element. The fiber web may be
adhered to the support layer(s) by any suitable means including,
for example, by lamination, point bonding, thermo-dot bonding,
ultrasonic bonding, calendering, use of adhesives (e.g., glue-web),
and/or co-pleating.
In some embodiments, the fiber web layer(s) along with the support
layer(s), if present, may be pleated (e.g., co-pleated). In some
such embodiments, the pleated layers may be positioned adjacent a
core (e.g., wrapped around a core).
The core can have any cross-sectional shape (circular, oval,
triangular, irregular, trapezoidal, square or rectangular, or the
like). The core may also have an aspect ratio (length to average
cross-sectional dimension) of at least 1:1, at least 2:1, more
typically at least 3:1, 5:1, or 10:1 or more. The fiber web may at
least partially or completely cover the core.
It has been discovered within the context of certain embodiments
described herein, that the oil repellency level of the fiber web
allows adequate coalescence to be achieved without increasing (or
minimally increasing) the resistance of the fiber web and/or the
overall filter media. Without wishing to be bound by any theory, it
is believed that tailoring the surface chemistry of the fiber web
(e.g., by modification of the fiber web and/or choosing appropriate
fiber materials) allows the fluid in the gas stream (e.g., the
fluid to be separated comprising an oil, lubricant, and/or cooling
agent, etc.) to favorably interact with the surface, such that the
surface energy density (or surface tension) is changed relative to
the surface energy density of fiber web. Having a similar surface
energy density between the fluids in the gas stream and the surface
of the fiber web causes the fluid to be separated to preferentially
associate with (e.g., wetting) the fiber web.
The fiber web may be tailored to have a particular oil repellency
level, e.g., in order to coalesce oil, lubricants, and/or cooling
agents from an gas stream passed through the fiber web. In some
embodiments, the oil repellency level of the fiber web is between 4
and 6 (e.g., 4-6, 4.5-5.5, 4.5-5, 5-5.5). In certain embodiments,
the oil repellency level of the fiber web is 4, 4.5, 5, 5.5 or 6.
Oil repellency level as described herein is determined according to
AATCC TM 118 (1997) measured at 23.degree. C. and 50% relative
humidity (RH). Briefly, 5 drops of each test oil (having an average
droplet diameter of about 2 mm) are placed on five different
locations on the surface of the fiber web. The test oil with the
greatest oil surface tension that does not wet (e.g.,. has a
contact angle greater than or equal to 90 degrees with the surface)
the surface of the fiber web after 30 seconds of contact with the
fiber web at 23.degree. C. and 50% RH, corresponds to the oil
repellency level (listed in Table 1). For example, if a test oil
with a surface tension of 26.6 mN/m does not wet (i.e. has a
contact angle of greater than or equal to 90 degrees with the
surface) the surface of the fiber web after 30 seconds, but a test
oil with a surface tension of 25.4 mN/m wets the surface of the
fiber web within thirty seconds, the fiber web has an oil
repellency level of 4. By way of another example, if a test oil
with a surface tension of 25.4 mN/m does not wet the surface of the
fiber web after 30 seconds, but a test oil with a surface tension
of 23.8 mN/m wets the surface of the fiber web within thirty
seconds, the fiber web has an oil repellency level of 5. By way of
yet another example, if a test oil with a surface tension of 23.8
mN/m does not wet the surface of the fiber web after 30 seconds,
but a test oil with a surface tension of 21.6 mN/m wets the surface
of the fiber web within thirty seconds, the fiber web has an oil
repellency level of 6. In some embodiments, if three or more of the
five drops partially wet the surface (e.g., forms a droplet, but
not a well-rounded drop on the surface) in a given test, then the
oil repellency level is expressed to the nearest 0.5 value
determined by subtracting 0.5 from the number of the test liquid.
By way of example, if a test oil with a surface tension of 25.4
mN/m does not wet the surface of the fiber web after 30 seconds,
but a test oil with a surface tension of 23.8 mN/m only partially
wets the surface of the fiber web after 30 seconds (e.g., three or
more of the test droplets form droplets on the surface of the fiber
web that are not well-rounded droplets) within thirty seconds, the
fiber web has an oil repellency level of 5.5.
TABLE-US-00001 TABLE 1 Oil Repellency Surface tension Level Test
Oil (in mN/m) 1 Kaydol (mineral oil) 31 2 65/35 Kaydol/n-hexadecane
28 3 n-hexadecane 27.5 4 n-tetradecane 26.6 5 n-dodecane 25.4 6
n-decane 23.8 7 n-octane 21.6 8 n-heptane 20.1
In some embodiments, as described in more detail below, the fiber
web may be used to decrease oil carry over of a filter media and/or
filter element. Briefly, oil carry over provides a measurement of
oil that is present in an gas stream comprising the oil, after the
gas stream has passed through the fiber web. The decreased oil
carry over may be achieved, in some embodiments, by tailoring the
surface chemistry of the fiber web (e.g., by surface modification
of a surface of the fiber web and/or by choosing a particular
surface chemistry of the plurality of fibers) to allow at least one
surface of the fiber web to interact with one or more components
(e.g., oil, lubricant, and/or cooling agents) in the gas stream.
The oil carry over may also be enhanced by the fiber web being
wrapped at least two times around a core. In certain embodiments,
the choice of surface chemistry (e.g., surface modification), fiber
diameter, mean flow pore size, and/or permeability of the fiber web
may cause the fluid to be to coalesced into droplets that may be
easily separated from the gas stream. In some embodiments, the
fiber web as described herein may be particularly well suited for
removing droplets of oil having a surface tension between 22 mN/m
and 33 mN/m measured at 23.degree. C. and 50% RH by the Du Nouy
ring method from an gas stream. In certain embodiments, the fiber
web may be particularly well suited for removing droplets having
relatively small diameters from the gas stream.
In certain embodiments, the filter media or filter element
described herein do not require separate stages of filter media,
wherein each stage serves a different purpose such as particle
separation, coalescence, and/or shedding. For example, a single
filter media can include one or more layers of fiber web that
perform two or more of these functions (particle separation,
coalescence, and/or shedding). However, in other embodiments,
different stages of media may be included.
In some embodiments, the fiber web and/or a plurality of fibers
within the fiber web may be modified to alter and/or enhance the
wettability of at least one surface of the fiber web with respect
to a particular fluid (e.g., oil). For instance, in some
embodiments, the surface modification may alter and/or enhance the
hydrophilicity and/or lipophilicity of at least one surface of the
fiber web. In one example, a surface of a relatively lipophobic (or
oleophobic) fiber web may be modified with a lipophilic material
(e.g., charged material, non-charged lipophilic material, organic
lipophilic material), such that the modified surface is lipophilic.
In some such cases, the fiber web may have a modified lipophilic
surface (e.g., upstream surface) and an unmodified lipophobic
surface (e.g., downstream surface). In other cases, the upstream
and downstream surfaces of the fiber web may be modified to be
lipophilic. Alternatively, in certain embodiments, a surface of a
relatively lipophilic fiber web may be modified with a lipophobic
material, such that the modified surface is lipophobic.
In certain embodiments, both the upstream and the downstream
surfaces of a fiber web are modified. In other embodiments, the
entire fiber web is modified. Although other surface modification
techniques can be used, in certain embodiments, a layer is modified
using chemical vapor deposition. For instance, the fiber web may
comprise a chemical vapor deposition coating.
Regardless of whether the surface is modified to lipophilic or
lipophobic, in general, at least one surface of the fiber web may
be modified to be wetting toward the fluid to be separated. In some
embodiments, at least one surface of the fiber web may be modified
to enhance its wettability with respect to a particular fluid.
In some embodiments, the fiber web may serve to decrease the
overall oil carry over of the filter media and/or a filter element
comprising the fiber web. For instance, the fiber web may be
configured to effectively coalesce the fluid to be separated such
that the filter media and/or a filter element may achieve a
particular oil carry over. Oil carry over, as described herein, is
measured according to ISO 12500 on a 6.times.10 cm fiber web with a
20 cm/s face velocity and a temperature of 40.degree. C., using a
Shell Corona S2 P100 test oil at a concentration of 0.2 g/m.sup.3.
In certain embodiments, the fiber web has an oil carry over of less
than or equal to 5000 mg/m.sup.3, less than or equal to 4000
mg/m.sup.3, less than or equal to 3000 mg/m.sup.3, less than or
equal to 2500 mg/m.sup.3, less than or equal to 2000 mg/m.sup.3,
less than or equal to 1500 mg/m.sup.3, less than or equal to 1000
mg/m.sup.3, less than or equal to 500 mg/m.sup.3, less than or
equal to 250 mg/m.sup.3, or less than or equal to 100 mg/m.sup.3.
In some embodiments, the fiber web has an oil carry over of greater
than or equal to 0 mg/m.sup.3, greater than or equal to 100
mg/m.sup.3, greater than or equal to 250 mg/m.sup.3, greater than
or equal to 500 mg/m.sup.3, greater than or equal to 1000
mg/m.sup.3, greater than or equal to 1500 mg/m.sup.3, greater than
or equal to 2000 mg/m.sup.3, greater than or equal to 2500
mg/m.sup.3, greater than or equal to 3000 mg/m.sup.3, or greater
than or equal to 4000 mg/m.sup.3. Combinations of the
above-referenced ranges are also possible (e.g., greater than or
equal to 0 mg/m.sup.3 and less than or equal to 5000 mg/m.sup.3).
Other ranges of oil carry over are also possible.
In certain embodiments, a fiber web described herein has an oil
carry over percentage of less than 20%. Oil carry over percentage,
as described herein, is a measurement of oil that is present in an
gas stream comprising the oil, after the gas stream has passed
through the fiber web, as a percentage of total oil present in the
gas stream prior to passing through the fiber web. The oil carry
over percentage is determined by measuring oil carry over values as
described above. In some embodiments, the fiber web has an oil
carry over percentage of less than or equal to 20%, less than or
equal to 15%, less than or equal to 10%, less than or equal to 5%,
less than or equal to 3%, less than or equal to 2%, or less than or
equal to 1%. In certain embodiments, the fiber web has an oil carry
over percentage of greater than or equal to 0%, greater than or
equal to 1%, greater than or equal to 2%, greater than or equal to
3%, greater than or equal to 5%, greater than or equal to 10%, or
greater than or equal to 15%. Combinations of the above-referenced
ranges are also possible (e.g., less than or equal to 20% and
greater than or equal to 0%, less than or equal to 3% and greater
than or equal to 0%). Other values of oil carry over percentage are
also possible.
In some embodiments, the fiber web may be perforated, i.e the fiber
web may comprise a plurality of perforations. In certain
embodiments the fiber web may include a plurality of perforations
as shown illustratively in FIG. 4. The perforations may, in some
embodiments, reduce the overall pressure drop of the filter
media/filter element and/or impart a relatively high air
permeability while allowing the fiber web to maintain good oil
coalescence characteristics. When multiple layers are present, the
perforations may be positioned such that perforations between
adjacent layers of fiber web do not align, e.g., when layered on a
planar surface or wrapped around a core. While much of the
description herein relates to a fiber web wrapped around a core, in
some embodiments, a filter element or filter media comprises a
perforated fiber web without a core. However, in alternative
embodiments, the perforated fiber web may be wrapped around a core,
as described above.
In some embodiments, perforating a fiber web may result in a
plurality of holes through the full thickness of the fiber web. In
one embodiment, a plurality of perforations, as shown
illustratively in a cross-section of fiber web 110 in FIG. 4, may
define a plurality of perforations or holes 115. In certain
embodiments, a perforation may have defined attributes, such as
shape, size, aspect ratio, length, and/or width. For example, each
perforation in the plurality of perforations may have a defined
shape, which may be, for example, substantially circular, square,
rectangular, trapezoidal, polygonal or oval in cross-section and/or
in plane view (i.e., viewed from above). The shapes may be regular
or irregular. Other shapes are also possible.
In some instances, the average largest cross-sectional dimension of
the perforations (e.g., average diameter of the holes) may be
measured at a surface of the fiber web including the perforations.
For instance, in some embodiments, the average largest
cross-sectional dimension (e.g., diameter) may be greater than or
equal to about 1 mm, greater than or equal to about 2 mm, greater
than or equal to about 3 mm, greater than or equal to about 6 mm,
greater than or equal to about 10 mm, greater than or equal to
about 20 mm, greater than or equal to about 40 mm, greater than or
equal to about 60 mm, greater than or equal to about 80 mm, or
greater than or equal to about 90 mm. In certain embodiments, the
average largest cross-sectional dimension may be less than or equal
to about 100 mm, less than or equal to about 90 mm, less than or
equal to about 80 mm, less than or equal to about 60 mm, less than
or equal to about 40 mm, less than or equal to about 20 mm, less
than or equal to about 10 mm, less than or equal to about 6 mm,
less than or equal to about 3 mm, or less than or equal to about 2
mm. Combinations of the above-referenced ranges are also possible
(e.g., greater than or equal to about 1 mm and less than or equal
to about 100 mm, greater than or equal to about 6 mm and less than
or equal to about 60 mm.). Other values of average largest
cross-sectional dimensions of the perforations are also possible.
Those skilled in the art would be capable of selecting a suitable
method for determining the average largest cross-sectional
dimension of the perforations including, for example, taking the
average of at least 10 perforation largest cross-sectional
dimensions measured using a handheld micrometer.
The perforations may also be characterized by the surface area
coverage of the perforations (e.g., as a percentage of the surface
area of the fiber web comprising perforations). In certain
embodiments, the perforations may cover a certain percentage of the
surface area of a layer (i.e., the combined surface area of the
perforations as a percentage of the total area of the layer as
measured by its length times width). For instance, in some
embodiments, the perforations may cover greater than or equal to
about 0%, greater than or equal to about 1%, greater than or equal
to about 2%, greater than or equal to about 5%, greater than or
equal to about 8%, greater than or equal to about 10%, greater than
or equal to about 15%, greater than or equal to about 20%, greater
than or equal to about 25%, greater than or equal to about 30%, or
greater than or equal to about 40% of the surface area of the
layer. In some instances, perforations may cover less than or equal
to about 50%, less than or equal to about 40%, less than or equal
to about 30%, less than or equal to about 25%, less than or equal
to about 20%, less than or equal to about 15%, less than or equal
to about 10%, less than or equal to about 5%, less than or equal to
about 2%, or less than or equal to about 1% of the surface area of
the layer. Combinations of the above-referenced ranges are also
possible (e.g., greater than or equal to about 0% and less than or
equal to about 50%, greater than or equal to about 2% and less than
or equal to about 10%). Other ranges of coverage are also
possible.
In embodiments, the perforations may be arranged such that a
defined periodicity (i.e., distance between the geometric centers
of neighboring perforations) and/or pattern exists in the layer.
The periodicity may be measured in the machine direction and/or in
the cross direction. In some embodiments, the perforations may have
an average periodicity of greater than or equal to about 2 mm,
greater than or equal to about 5 mm, greater than or equal to about
10 mm, greater than or equal to about 12 mm, greater than or equal
to about 15 mm, greater than or equal to about 20 mm, or greater
than or equal to about 28 mm. In some instances, the perforations
may have an average periodicity of less than or equal to about 30
mm, less than or equal to about 22 mm, less than or equal to about
18 mm, less than or equal to about 14 mm, less than or equal to
about 10 mm, or less than or equal to about 6 mm. Combinations of
the above-referenced ranges are also possible (e.g., greater than
or equal to about 5 mm and less than or equal to about 20 mm).
Other values of average periodicity are also possible.
In some embodiments, the periodicity of the perforations may be
regular across the layer. In other embodiments, the periodicity of
the perforations may be irregular and/or may vary based on a
certain factors, such as location in the layer or the pattern of
the perforations. In certain embodiments, the plurality of
perforations may be arranged to form a pattern (e.g., simple,
checkerboard, honeycomb, cubic, hexagonal, polygonal).
In general, any suitable pattern can be used to achieve the desired
properties. It should be noted, however, that the plurality of
perforations may not have a defined pattern and/or periodicity in
some embodiments.
In general the plurality of perforations may be formed by any
suitable process. For instance, for a dry web, a plurality of
perforations may be formed by a thermo-mechanical process (e.g.,
thermo-dot bonder, needle punch perforation) or a mechanical
process (e.g., puncture or hydro-entangling). For a wet web, for
example, a plurality of perforations may be formed by using a
perforating Dandy-roll or by hydro-entangling. In a thermo-dot
bonder, a thermo-mechanical element applies heat and force to a
fiber web to create perforations. Puncture and Dandy roll processes
involve the application of mechanical force on a wet layer during
drying to make the perforations. Hydro-entangling makes
perforations in a fiber web through the application of
hydro-mechanical force on a wet or dry layer. In some cases, the
application of thermal energy (e.g., a laser) can be used to form
perforations. Those skilled in the art would be capable of
selecting other suitable means for perforating a fiber web based
upon the teachings of the specification including, for example,
stamping, cutting, and introducing the perforations during
production. Other means are also possible.
In some embodiments, it should be understood that the fiber web
need not include any perforations.
In some embodiments, the filter element comprises one or more
additional layers (e.g., a support layer). For example, as
illustrated in FIG. 5, filter element 104 comprises fiber web 110
wrapped around core 120 (e.g., such that the fiber web forms at
least two layers around the core) and an additional layer 130
directly adjacent (e.g., wrapped around) fiber web 110. In some
embodiments, as illustrated in FIG. 5, the additional layer may be
wrapped around the fiber web (e.g., an outer surface of the fiber
web). In other embodiments, however, the one or more additional
layers may be in contact with, but not wrapped around, the fiber
web.
In some embodiments, the one or more additional layers may be
disposed between the core and the fiber web. For example, as
illustrated in FIG. 6, filter element 108 comprises additional
layer 130 (e.g., a support layer) directly adjacent (e.g., wrapped
around) core 120. In some such embodiments, fiber web 110 may be
wrapped around additional layer 130.
In some embodiments, the filter element may comprise at least 1, at
least 2, at least 3, at least 4, at least 5, at least 7, at least
9, at least 10, at least 11, at least 13, at least 15, at least 17,
or at least 19 layers of the support layer wrapped around the fiber
web and/or wrapped around the core. In certain embodiments, the
filter element comprises less than or equal to 20, less than or
equal to 19, less than or equal to 17, less than or equal to 15,
less than or equal to 13, less than or equal to 13, less than or
equal to 11, less than or equal to 10, less than or equal to 9,
less than or equal to 7, less than or equal to 5, less than or
equal to 4, less than or equal to 3, or less than or equal to 2
layers of the support layer wrapped around the fiber web and/or
wrapped around the core. Combinations of the above-referenced
ranges are also possible (e.g., at least 1 layer and less than or
equal to 20 layers, at least 2 layers and less than or equal to 13
layers, at least 2 layers and less than or equal to 4 layers, at
least 5 layers and less than or equal to 10 layers). Other ranges
are also possible.
In other embodiments, the filter element may comprise at least 1,
at least 2, at least 3, at least 4, at least 5, at least 7, at
least 9, at least 10, at least 11, at least 13, at least 15, at
least 17, or at least 19 layers of the fiber web wrapped around a
support layer and/or wrapped around a core. In certain embodiments,
the filter element comprises less than or equal to 20, less than or
equal to 19, less than or equal to 17, less than or equal to 15,
less than or equal to 13, less than or equal to 13, less than or
equal to 11, less than or equal to 10, less than or equal to 9,
less than or equal to 7, less than or equal to 5, less than or
equal to 4, less than or equal to 3, or less than or equal to 2
layers of the fiber web wrapped around the support layer and/or
wrapped around the core. Combinations of the above-referenced
ranges are also possible (e.g., at least 1 layer and less than or
equal to 20 layers, at least 2 layers and less than or equal to 13
layers, at least 2 layers and less than or equal to 4 layers, at
least 5 layers and less than or equal to 10 layers). Other ranges
are also possible.
In an alternative embodiment, the filter element does not comprise
a core. For example, the fiber web may be, in some embodiments,
cast and wrapped around a removable core (e.g., a sieve) such that
the filter element comprises at least two layers of the fiber web
wrapped around itself.
In certain embodiments, one or more additional layers directly
adjacent the fiber web may facilitate the drainage of a fluid
(e.g., an oil) from the fiber web.
As described herein, in some embodiments, an gas stream comprising
the fluid (e.g., comprising an oil, lubricant, and/or cooling
agent) is filtered using a filter media/filter element described
herein by passing the gas stream including the oil, lubricant,
and/or cooling agent through the fiber web (or through a filter
element comprising the fiber web, optionally wrapped around a
core).
In some embodiments, a filter media or filter element described
herein is tailored for filtering a fluid (e.g., oil, lubricant,
and/or cooling agent) having a particular surface tension from an
gas stream. For example, the fiber webs described herein (e.g.,
having an oil repellency level of between 4 to 6) may be well
suited for filtration of oils, lubricants, cooling agents or other
fluids having a surface tension of greater than or equal to 22 mN/m
and less than or equal to 33 mN/m at 23.degree. C. and 50% RH (or
greater than or equal to 23.8 mN/m and less than or equal to 26.6
mN/m). In some embodiments, the fluid (e.g., the fluid present in
the gas stream) has a surface tension of greater than or equal to
22 mN/m, greater than or equal to 24 mN/m, greater than or equal to
26 mN/m, greater than or equal to 28 mN/m, greater than or equal to
30 mN/m, or greater than or equal to 32 mN/m as determined at
23.degree. C. and 50% RH by the Du Nouy ring method. In certain
embodiments, the fluid has a surface tension of less than or equal
to 33 mN/m, less than or equal to 32 mN/m, less than or equal to 30
mN/m, less than or equal to 28 mN/m, less than or equal to 26 mN/m,
or less than or equal to 24 mN/m as determined at 23.degree. C. and
50% RH by the Du Nouy ring method. Combinations of the
above-referenced ranges are also possible (e.g., greater than or
equal to 22 mN/m and less than or equal to 33 mN/m). Other surface
tensions of the fluid determined at 23.degree. C. and 50% RH are
also possible.
In some embodiments, the fluid (e.g., the fluid present in the gas
stream to be filtered by the fiber web, filter element, and/or
filter media) has a surface tension of greater than or equal to
23.8 mN/m, greater than or equal to 24 mN/m, greater than or equal
to 24.5 mN/m, greater than or equal to 25 mN/m, greater than or
equal to 25.5 mN/m, greater than or equal to 26 mN/m, or greater
than or equal to 26.5 mN/m as determined at the filtration
temperature by the Du Nouy ring method. In certain embodiments, the
fluid has a surface tension of less than or equal to 26.6 mN/m,
less than or equal to 26.5 mN/m, less than or equal to 26 mN/m,
less than or equal to 25.5 mN/m, less than or equal to 25 mN/m,
less than or equal to 24.5 mN/m, or less than or equal to 24 mN/m
as determined at the filtration temperature by the Du Nouy ring
method. Combinations of the above-referenced ranges are also
possible (e.g., greater than or equal to 23.8 mN/m and less than or
equal to 26.6 mN/m). Other surface tensions of the fluid determined
at the filtration temperature are also possible.
The filtration temperature, as used herein, generally refers the
temperature of the gas stream comprising the fluid that is being
filtered by a filter element, filter media, and/or fiber web
described herein. In some embodiments, the filtration temperature
is greater than or equal to 40.degree. C., greater than or equal to
50.degree. C., greater than or equal to 60.degree. C., greater than
or equal to 70.degree. C., greater than or equal to 80.degree. C.,
greater than or equal to 90.degree. C., greater than or equal to
100.degree. C. greater than or equal to 110.degree. C., greater
than or equal to 120.degree. C., greater than or equal to
130.degree. C., or greater than or equal to 140.degree. C. In
certain embodiments, the filtration temperature is less than or
equal to 150.degree. C., less than or equal to 140.degree. C., less
than or equal to 130.degree. C., less than or equal to 120.degree.
C., less than or equal to 110.degree. C., less than or equal to
100.degree. C., less than or equal to 90.degree. C., less than or
equal to 80.degree. C., less than or equal to 70.degree. C., less
than or equal to 60.degree. C., or less than or equal to 50.degree.
C. Combinations of the above-referenced ranges are also possible
(e.g., greater than or equal to 70.degree. C. and less than or
equal to 150.degree. C., greater than or equal to 40.degree. C. and
less than or equal to 150.degree. C.). Other filtration
temperatures are also possible.
Non-limiting examples of fluids that may be filtered (e.g.,
coalesced) by the fiber webs (or filter elements comprising the
fiber webs) described herein include oils, lubricants, cooling
agents, and combinations thereof. Non-limiting examples of
oils/lubricants that may be filtered (e.g., coalesced) by the fiber
webs described herein include alkanes (e.g., n-heptane, n-octane,
n-decane, n-dodecane, n-etradecane, n-hexadecane), polyphenyl
ethers (e.g., four-ring polyphenyl ethers, five-ring polyphenyl
ethers, modified polyphenyl ethers), glycols and derivatives
thereof, paraffinic oils, mineral oil (e.g., naphthenic mineral
oils, paraffinic mineral oils) fluorosilicones, fluorinated
polyethers, glycerol, castor oil, and combinations thereof. Those
skilled in the art would understand based upon the teachings of
this specification that these examples are not intended to be
limiting and that additional oils, lubricants, cooling agents, and
combinations thereof are also possible. For example, the oils,
lubricants, cooling agents, and combinations thereof may include
engine oils, liquid compounds of natural and refined gas, fractions
of distillation columns with liquid and/or gas mixtures, food-based
oils, liquid and gas streams from fracking, droplets of mercury and
its alloys, polymer/oligomer/monomer droplets (e.g., in the
ventilation of chemical plants), condensed liquid from exhaust
systems, or the like. As described above, in some embodiments, the
fluid to be filtered by the fiber webs described herein have a
particular surface tension (e.g., between 22 mN/m and 33 mN/m at
23.degree. C. at 50% RH).
In some embodiments, the fiber web may include glass fibers (e.g.,
microglass fibers, chopped strand glass fibers, or a combination
thereof). Microglass fibers and chopped strand glass fibers are
known to those skilled in the art. One skilled in the art is able
to determine whether a glass fiber is microglass or chopped strand
by observation (e.g., optical microscopy, electron microscopy).
Microglass fibers may also have chemical differences from chopped
strand glass fibers. In some cases, though not required, chopped
strand glass fibers may contain a greater content of calcium or
sodium than microglass fibers. For example, chopped strand glass
fibers may be close to alkali free with high calcium oxide and
alumina content. Microglass fibers may contain 10-15% alkali (e.g.,
sodium, magnesium oxides) and have relatively lower melting and
processing temperatures. The terms refer to the technique(s) used
to manufacture the glass fibers. Such techniques impart the glass
fibers with certain characteristics. In general, chopped strand
glass fibers are drawn from bushing tips and cut into fibers in a
process similar to textile production. Chopped strand glass fibers
are produced in a more controlled manner than microglass fibers,
and as a result, chopped strand glass fibers will generally have
less variation in fiber diameter and length than microglass fibers.
Chopped strand diameters tend to follow a normal distribution.
Though, it can be appreciated that chopped strand glass fibers may
be provided in any appropriate average diameter distribution (e.g.,
Gaussian distribution). Microglass fibers are drawn from bushing
tips and further subjected to flame blowing or rotary spinning
processes. In some cases, fine microglass fibers may be made using
a remelting process. In this respect, microglass fibers may be fine
or coarse. As used herein, fine microglass fibers are less than or
equal to 1 micron in diameter and coarse microglass fibers are
greater than or equal to 1 micron in diameter.
In some embodiments, the average diameter of the glass fibers may
be greater than or equal to about 0.01 microns, greater than or
equal to about 0.1 microns, greater than or equal to about 0.4
microns, greater than or equal to about 0.5 microns, greater than
or equal to about 1 micron, greater than or equal to about 2
microns, greater than or equal to about 5 microns, greater than or
equal to about 10 microns, greater than or equal to about 15
microns, greater than or equal to about 20 microns, greater than or
equal to about 30 microns, or greater than or equal to about 40
microns. In some instances, the glass fibers may have an average
fiber diameter of less than or equal to about 50 microns, less than
or equal to about 40 microns, less than or equal to about 30
microns, less than or equal to about 25 microns, less than or equal
to about 20 microns, less than or equal to about 15 microns, less
than or equal to about 10 microns, less than or equal to about 5
microns, less than or equal to about 2 microns, less than or equal
to about 1 micron, less than or equal to about 0.5 microns, less
than or equal to about 0.4 microns, or less than or equal to about
0.1 microns. Combinations of the above-referenced ranges are also
possible (e.g., greater than or equal to about 0.01 microns and
less than or equal to about 50 microns, greater than or equal to
about 0.4 microns and less than or equal to about 10 microns).
Other values of average fiber diameter are also possible. In some
embodiments, glass fibers may have a length in the range of between
about 0.05 mm and about 50 mm. In some embodiments, the average
length of the glass fibers may be less than or equal to about 50
mm, less than or equal to about 40 mm, less than or equal to about
30 mm, less than or equal to about 25 mm, less than or equal to
about 20 mm, less than or equal to about 10 mm, less than or equal
to about 5 mm, less than or equal to about 1 mm, less than or equal
to about 0.5 mm, less than or equal to about 0.3 mm, or less than
or equal to about 0.1 mm. In certain embodiments, the average
length of the glass fibers may be greater than or equal to about
0.05 mm, greater than or equal to about 0.1 mm, greater than or
equal to about 0.3 mm, greater than or equal to about 0.5 mm,
greater than or equal to about 1 mm, greater than or equal to about
5 mm, greater than or equal to about 10 mm, greater than or equal
to about 20 mm, greater than or equal to about 25 mm, greater than
or equal to about 30 mm, or greater than or equal to about 40 mm.
Combinations of the above-referenced ranges are also possible
(e.g., greater than or equal to about 0.05 mm and less than or
equal to about 50 mm, greater than or equal to about 0.3 mm and
less than or equal to about 20 mm). Other values of average length
are also possible.
It should be appreciated that the above-noted dimensions are not
limiting and that the microglass and/or chopped strand fibers, as
well as the other fibers described herein, may also have other
dimensions.
In some embodiments, the fiber web (and/or one or more additional
layers, such as support layers) in the filter media may include
synthetic fibers. Synthetic fibers may include any suitable type of
synthetic polymer. Examples of suitable synthetic fibers include
staple fibers, polyesters (e.g., polyethylene terephthalate,
polybutylene terephthalate), polycarbonate, polyamides (e.g.,
various nylon polymers), polyaramid (e.g., Kevlar.RTM.,
Nomex.RTM.), polyimide, polyphenylene sulfide, polyphenylene oxide,
polyethylene, polypropylene, polyether ether ketone, polyolefin,
acrylics, polyvinyl alcohol, regenerated cellulose (e.g., synthetic
cellulose such Lyocell, rayon), polyacrylonitriles, polyvinylidene
fluoride (PVDF), copolymers of polyethylene and PVDF, polyether
sulfones, halogenated polymers, and combinations thereof. In some
embodiments, the synthetic fibers are organic polymer fibers.
Synthetic fibers may also include multi-component fibers (i.e.,
fibers having multiple compositions such as bicomponent fibers). In
some cases, synthetic fibers may include meltblown, meltspun, melt
electrospun, solvent electrospun, or centrifugal spun fibers, which
may be formed of polymers described herein (e.g., polyester,
polypropylene). In other cases, synthetic fibers may be electrospun
fibers. The fiber web may also include combinations of more than
one type of synthetic fiber. It should be understood that other
types of synthetic fiber types may also be used.
In some embodiments, the average diameter of the synthetic fibers
in the fiber web may be, for example, greater than or equal to
about 0.5 microns, greater than or equal to about 0.6 microns,
greater than or equal to about 1 micron, greater than or equal to
about 2 microns, greater than or equal to about 3 microns, greater
than or equal to about 4 microns, greater than or equal to about 6
microns, greater than or equal to about 8 microns, greater than or
equal to about 10 microns, greater than or equal to about 15
microns, greater than or equal to about 20 microns, greater than or
equal to about 30 microns, or greater than or equal to about 40
microns. In some instances, the synthetic fibers may have an
average diameter of less than or equal to about 50 microns, less
than or equal to about 40 microns, less than or equal to about 30
microns, less than or equal to about 20 microns, less than or equal
to about 15 microns, less than or equal to about 10 microns, less
than or equal to about 8 microns, less than or equal to about 6
microns, less than or equal to about 4 microns, less than or equal
to about 3 microns, less than or equal to about 2 microns, less
than or equal to about 1 micron, or less than or equal to about 0.6
microns. Combinations of the above-referenced ranges are also
possible (e.g., greater than or equal to about 0.5 micron and less
than or equal to about 50 microns, greater than or equal to about
0.6 microns and less than or equal to about 20 microns). Other
values of average fiber diameter are also possible.
In some cases, the synthetic fibers in the fiber web may have an
average length of greater than or equal to about 0.25 mm, greater
than or equal to about 0.5 mm, greater than or equal to about 1 mm,
greater than or equal to about 2 mm, greater than or equal to about
4 mm, greater than or equal to about 6 mm, greater than or equal to
about 8 mm, greater than or equal to about 10 mm, greater than or
equal to about 15 mm, or greater than or equal to about 20 mm. In
some instances, synthetic fibers may have an average length of less
than or equal to about 30 mm, less than or equal to about 20 mm,
less than or equal to about 15 mm, less than or equal to about 10
mm, less than or equal to about 8 mm, less than or equal to about 6
mm, less than or equal to about 4 mm, less than or equal to about 2
mm, less than or equal to about 1 mm, or less than or equal to
about 0.5 mm. Combinations of the above-referenced ranges are also
possible (e.g., greater than or equal to about 0.25 mm and less
than or equal to about 25 mm, greater than or equal to about 3 mm
and less than or equal to about 15 mm). Other values of average
fiber length are also possible.
In some embodiments, a filter media, filter element, fiber web
and/or one or more additional layers described herein may comprise
binder fibers (e.g., bicomponent fibers). The binder fibers can be
formed, for example, from any material that is effective to
facilitate thermal bonding between the fiber web and the support
layer, and will thus have an activation temperature that is lower
than the melting temperature of any non-binder fibers. The binder
fibers can be monocomponent fibers or any one of a number of
bicomponent binder fibers. In one embodiment, the binder fibers can
be bicomponent fibers, and each component can have a different
melting temperature. For example, the binder fibers can include a
core and a sheath where the activation temperature of the sheath is
lower than the melting temperature of the core. This allows the
sheath to melt prior to the core, such that the sheath binds to
other fibers in the layer, while the core maintains its structural
integrity. This may be particularly advantageous in that it creates
a more cohesive layer for trapping filtrate. The core/sheath binder
fibers can be concentric or non-concentric, and exemplary
core/sheath binder fibers can include the following: a polyester
core/copolyester sheath, a polyester core/polyethylene sheath, a
polyester core/polypropylene sheath, a polypropylene
core/polyethylene sheath, a polyamide core/polyethylene sheath, and
combinations thereof. Other exemplary bicomponent binder fibers can
include split fiber fibers, side-by-side fibers, and/or "island in
the sea" fibers. In an exemplary embodiment, the binder fiber
comprises polyvinylalcohol (e.g., as a dissolving fiber). The
binder fibers may comprise a thermoplastic polymer. The average
diameter of the binder fibers may be, for example, greater than or
equal to about 0.5 microns, greater than or equal to about 0.6
microns, greater than or equal to about 1 micron, greater than or
equal to about 2 microns, greater than or equal to about 3 microns,
greater than or equal to about 4 microns, greater than or equal to
about 6 microns, greater than or equal to about 8 microns, greater
than or equal to about 10 microns, greater than or equal to about
15 microns, greater than or equal to about 20 microns, greater than
or equal to about 30 microns, or greater than or equal to about 40
microns. In some instances, the binder fibers may have an average
diameter of less than or equal to about 50 microns, less than or
equal to about 40 microns, less than or equal to about 30 microns,
less than or equal to about 20 microns, less than or equal to about
15 microns, less than or equal to about 10 microns, less than or
equal to about 8 microns, less than or equal to about 6 microns,
less than or equal to about 4 microns, less than or equal to about
3 microns, less than or equal to about 2 microns, less than or
equal to about 1 micron, or less than or equal to about 0.6
microns. Combinations of the above-referenced ranges are also
possible (e.g., greater than or equal to about 0.5 micron and less
than or equal to about 50 microns, greater than or equal to about
0.6 microns and less than or equal to about 20 microns). Other
values of average fiber diameter are also possible.
In some cases, the binder fibers in the fiber web may have an
average length of greater than or equal to about 0.25 mm, greater
than or equal to about 0.5 mm, greater than or equal to about 1 mm,
greater than or equal to about 2 mm, greater than or equal to about
4 mm, greater than or equal to about 6 mm, greater than or equal to
about 8 mm, greater than or equal to about 10 mm, greater than or
equal to about 15 mm, or greater than or equal to about 20 mm. In
some instances, binder fibers may have an average length of less
than or equal to about 30 mm, less than or equal to about 20 mm,
less than or equal to about 15 mm, less than or equal to about 10
mm, less than or equal to about 8 mm, less than or equal to about 6
mm, less than or equal to about 4 mm, less than or equal to about 2
mm, less than or equal to about 1 mm, or less than or equal to
about 0.5 mm. Combinations of the above-referenced ranges are also
possible (e.g., greater than or equal to about 0.25 mm and less
than or equal to about 25 mm, greater than or equal to about 3 mm
and less than or equal to about 15 mm). Other values of average
fiber length are also possible.
The fiber web may comprise a suitable percentage of binder fibers.
For example, in some embodiments, the weight percentage of binder
fibers present in the fiber web may be at least about 0 wt %, at
least about 2 wt %, at least about 5 wt %, at least about 7 wt %,
or at least about 10 wt %. In certain embodiments, the weight
percentage of binder fibers present in the fiber web may be less
than or equal to about 15 wt %, less than or equal to about 10 wt
%, less than or equal to about 7 wt %, less than or equal to about
5 wt %, or less than or equal to about 2 wt %. Combinations of the
above-referenced ranges are also possible (e.g., at least about 0
wt % and less than or equal to about 10 wt %). Other ranges are
also possible.
In some embodiments, the fiber web may include one or more
cellulose fibers, such as softwood fibers, hardwood fibers, a
mixture of hardwood and softwood fibers, regenerated cellulose
fibers, and mechanical pulp fibers (e.g., groundwood, chemically
treated mechanical pulps, and thermomechanical pulps). Exemplary
softwood fibers include fibers obtained from mercerized southern
pine (e.g., mercerized southern pine fibers or "HPZ fibers"),
northern bleached softwood kraft (e.g., fibers obtained from Robur
Flash ("Robur Flash fibers")), southern bleached softwood kraft
(e.g., fibers obtained from Brunswick pine ("Brunswick pine
fibers")), or chemically treated mechanical pulps ("CTMP fibers").
For example, HPZ fibers can be obtained from Buckeye Technologies,
Inc., Memphis, Tenn.; Robur Flash fibers can be obtained from
Rottneros AB, Stockholm, Sweden; and Brunswick pine fibers can be
obtained from Georgia-Pacific, Atlanta, Ga. Exemplary hardwood
fibers include fibers obtained from Eucalyptus ("Eucalyptus
fibers"). Eucalyptus fibers are commercially available from, e.g.,
(1) Suzano Group, Suzano, Brazil ("Suzano fibers"), (2) Group
Portucel Soporcel, Cacia, Portugal ("Cacia fibers"), (3) Tembec,
Inc., Temiscaming, QC, Canada ("Tarascon fibers"), (4) Kartonimex
Intercell, Duesseldorf, Germany, ("Acacia fibers"), (5)
Mead-Westvaco, Stamford, Conn. ("Westvaco fibers"), and (6)
Georgia-Pacific, Atlanta, Ga. ("Leaf River fibers").
The average diameter of the cellulose fibers in the fiber web may
be, for example, greater than or equal to about 1 micron, greater
than or equal to about 2 microns, greater than or equal to about 3
microns, greater than or equal to about 4 microns, greater than or
equal to about 5 microns, greater than or equal to about 8 microns,
greater than or equal to about 10 microns, greater than or equal to
about 15 microns, greater than or equal to about 20 microns,
greater than or equal to about 30 microns, or greater than or equal
to about 40 microns. In some instances, the cellulose fibers may
have an average diameter of less than or equal to about 50 microns,
less than or equal to about 40 microns, less than or equal to about
30 microns, less than or equal to about 20 microns, less than or
equal to about 15 microns, less than or equal to about 10 microns,
less than or equal to about 7 microns, less than or equal to about
5 microns, less than or equal to about 4 microns, or less than or
equal to about 2 microns. Combinations of the above-referenced
ranges are also possible (e.g., greater than or equal to about 1
micron and less than or equal to about 5 microns). Other values of
average fiber diameter are also possible.
In some embodiments, the cellulose fibers may have an average
length. For instance, in some embodiments, cellulose fibers may
have an average length of greater than or equal to about 0.5 mm,
greater than or equal to about 1 mm, greater than or equal to about
2 mm, greater than or equal to about 3 mm, greater than or equal to
about 4 mm, greater than or equal to about 5 mm, greater than or
equal to about 6 mm, or greater than or equal to about 8 mm. In
some instances, cellulose fibers may have an average length of less
than or equal to about 10 mm, less than or equal to about 8 mm,
less than or equal to about 6 mm, less than or equal to about 4 mm,
less than or equal to about 2 mm, or less than or equal to about 1
mm. Combinations of the above-referenced ranges are also possible
(e.g., greater than or equal to about 1 mm and less than or equal
to about 3 mm). Other values of average fiber length are also
possible.
In general, the fiber web may include any suitable fiber type. In
some embodiments, the fiber web may include more than one type of
fiber. For example, in certain embodiments, the fiber web may
include one or more of a glass fiber, synthetic fiber, a
bicomponent fiber, and/or a cellulose fiber (e.g., regenerated,
Lyocell, etc.), as described herein.
In some embodiments, the fiber web may include glass fibers (e.g.,
microglass and/or chopped glass fibers). For instance, in some
embodiments, the weight percentage of the glass fibers in the fiber
web may be, for example, greater than or equal to about 0%, greater
than or equal to about 10%, greater than or equal to about 25%,
greater than or equal to about 50%, greater than or equal to about
75%, greater than or equal to 80%, greater than or equal to 90%,
greater than or equal to 95%, greater than or equal to 98%, or
greater than or equal to 99%. In some instances, the weight
percentage of the glass fibers in the fiber web may be less than or
equal to about 100%, less than or equal to about 75%, less than or
equal to about 50%, less than or equal to about 25%, less than or
equal to about 5%, or less than or equal to about 2%. Combinations
of the above-referenced ranges are also possible (e.g., greater
than or equal to about 0% and less than or equal to about 99%).
Other values of weight percentage of the glass in the fiber web are
also possible. In some embodiments, the fiber web includes 100%
glass fibers.
The ratio between the weight percentage of chopped strand glass
fibers and microglass fibers provides for different characteristics
in the filter media. In general, increasing the percentage of fine
glass fibers will increase the overall surface area of the filter
media; and, increasing the percentage of coarse glass fibers will
decrease the overall surface area of the filter media. Thus, in
general, increasing the amount of chopped strand glass fibers as
compared to the amount of microglass fibers decreases the overall
surface area of the filter media; and, increasing the amount of
microglass fibers as compared to the amount of chopped strand glass
fibers increases the surface area of the filter media. Increasing
the amount of chopped strand glass fibers within the filter media
also increases the pleatability of the filter media (i.e., the
ability of a filter to be pleated).
The percentage of chopped strand glass fibers and microglass fibers
(e.g., coarse and/or fine) within the filter media are selected to
provide desired characteristics.
Various percentages of chopped strand glass fibers can be included
within the glass fibers in the fiber web. In some embodiments,
chopped strand glass fibers may make up less than or equal to about
80% by weight of the glass fiber in the fiber web, less than about
75% by weight of the glass fiber in the fiber web, less than about
50% by weight of the glass fiber in the fiber web, less than about
40% by weight of the glass fiber in the fiber web, less than about
35% by weight of the glass fiber in the fiber web, less than about
25% by weight of the glass fiber in the fiber web, less than about
20% by weight of the glass fiber in the web, or less than about 3%
by weight of the glass fiber in the fiber web. In certain
embodiments, chopped strand glass fibers may make up greater than
about 0% by weight of the glass fiber in the fiber web, greater
than about 1% by weight of the glass fiber in the fiber web,
greater than about 3% by weight of the glass fiber in the fiber
web, greater than about 20% by weight of the glass fiber in the
fiber web, greater than about 25% by weight of the glass fiber in
the fiber web, greater than about 35% by weight of the glass fiber
in the fiber web, greater than about 40% by weight of the glass
fiber in the fiber web, greater than about 50% by weight of the
glass fiber in the fiber web, or greater than 75% by weight of the
glass fiber in the fiber web.
Combinations of the above-referenced ranges are also possible
(e.g., between about 1% by weight and about 50% by weight of the
glass fibers in the fiber web, between about 3% by weight and about
35% by weight of the glass fibers in the fiber web, or between
about 3% by weight and 25% by weight of the glass fibers in the
fiber web). In certain embodiments, substantially all of the glass
fibers in the fiber web are chopped strand glass fibers.
Additionally, different percentages of microglass fibers are
included within the glass fibers within the web. In some
embodiments, microglass fibers may make up greater than about 20%
by weight of the glass fibers in the fiber web, greater than about
25% by weight of the glass fibers in the fiber web, greater than
about 50% by weight of the glass fibers in the fiber web, greater
than about 60% by weight of the glass fibers in the fiber web,
greater than about 65% by weight of the glass fibers in the fiber
web, greater than about 75% by weight of the glass fibers in the
fiber web, greater than about 80% by weight of the glass fibers in
the fiber web, greater than about 97% by weight of the glass fibers
in the fiber web, or greater than about 99% by weight of the glass
fibers in the fiber web. In certain embodiments, microglass fibers
may make up less than about 100% by weight of the glass fibers in
the fiber web, less than about 99% by weight of the glass fibers in
the fiber web, less than about 97% by weight of the glass fibers in
the fiber web, less than about 80% by weight of the glass fibers in
the fiber web, less than about 75% by weight of the glass fibers in
the fiber web, less than about 65% by weight of the glass fibers in
the fiber web, less than about 60% by weight of the glass fibers in
the fiber web, less than about 50% by weight of the glass fibers in
the fiber web, less than about 25% by weight of the glass fibers in
the fiber web, or less than about 20% by weight of the glass fibers
in the fiber web. Combinations of the above-referenced ranges are
also possible (e.g., between about 45% by weight and about 97% by
weight of the glass fibers in the fiber web). Other ranges are also
possible.
Coarse microglass fibers, fine microglass fibers, or a combination
of microglass fibers thereof may be included within the glass
fibers of the web. For coarse microglass fibers, in some
embodiments, coarse microglass fibers may make up greater than or
equal to about 40%, greater than or equal to about 50%, greater
than or equal to about 60%, greater than or equal to about 70%,
greater than or equal to about 75%, or greater than or equal to
about 80% by weight of the total glass fibers in the fiber web. In
certain embodiments, coarse microglass fibers may make up less than
about 90%, less than about 80%, less than about 75%, less than
about 70%, less than about 60%, or less than about 50% by weight of
the total fibers in the fiber web. Combinations of the
above-referenced ranges are also possible (e.g., between about 40%
and about 90% by weight of the total fibers in the fiber web,
between about 75% and about 90% by weight of the total fibers in
the fiber web, or between about 60% and about 70% by weight of the
total fibers in the fiber web). Other ranges are also possible.
For fine microglass fibers, in some embodiments, fine microglass
fibers make up greater than or equal to about 0%, greater than or
equal to about 2%, greater than or equal to about 5%, greater than
or equal to about 10%, greater than or equal to about 12%, greater
than or equal to about 15% or greater than or equal to about 20% by
weight of the total fibers in the fiber web. In certain
embodiments, fine microglass fibers make up less than about 25%,
less than about 20%, less than about 15%, less than about 12%, less
than about 10%, less than about 5%, or less than about 2% by weight
of the total fibers in the fiber web. Combinations of the
above-referenced ranges are also possible (e.g., between about 0%
and about 25% by weight of the totalfibers in the fiber web,
between about 5% and about 10% by weight of the totalfibers in the
fiber web, or between about 2% and about 12% by weight of the
totalfibers in the fiber web). Other ranges are also possible.
In some embodiments in which synthetic fibers are included in the
fiber web, the weight percentage of synthetic fibers in the fiber
web may be greater than or equal to about 1%, greater than or equal
to about 3%, greater than or equal to about 5%, greater than or
equal to about 10%, greater than or equal to about 20%, greater
than or equal to about 40%, greater than or equal to about 60%,
greater than or equal to about 80%, greater than or equal to about
90%, or greater than or equal to about 95%. In some instances, the
weight percentage of synthetic fibers in the fiber web may be less
than or equal to about 100%, less than or equal to about 98%, less
than or equal to about 85%, less than or equal to about 75%, less
than or equal to about 50%, less than or equal to about 10%, less
than or equal to about 5%, less than or equal to about 3%, or less
than or equal to about 1%. Combinations of the above-referenced
ranges are also possible (e.g., greater than or equal to about 1%
and less than or equal to about 100%, greater than or equal to
about 80% and less than or equal to about 100%). Other values of
weight percentage of synthetic fibers in the fiber web are also
possible. In some embodiments, the fiber web includes 100%
synthetic fibers. In other embodiments, the fiber web may include
0% synthetic fibers.
In certain embodiments, the fiber web may optionally include
cellulose fibers, such as regenerated cellulose (e.g., rayon,
Lyocell), fibrillated synthetic fibers, microfibrillated cellulose,
and natural cellulose fibers (e.g., hardwood, softwood). For
instance, in some embodiments, the weight percentage of cellulose
fibers in the fiber web may be greater than or equal to about 1%,
greater than or equal to about 5%, greater than or equal to about
10%, greater than or equal to about 15%, greater than or equal to
about 45%, greater than or equal to about 65%, or greater than or
equal to about 90%. In some instances, the weight percentage of the
cellulose fibers in the fiber web may be less than or equal to
about 100%, less than or equal to about 85%, less than or equal to
about 55%, less than or equal to about 20%, less than or equal to
about 10%, or less than or equal to about 2%. Combinations of the
above-referenced ranges are also possible (e.g., greater than or
equal to about 1% and less than or equal to about 100%). Other
values of weight percentage of the cellulose fibers in the fiber
web are also possible. In some embodiments, the fiber web includes
100% cellulose fibers. In other embodiments, the fiber web may
include 0% cellulose fibers.
As noted above, in some embodiments at least one surface of the
fiber web may be modified such that the fiber web has an oil
repellency level of between 4 and 6. In some embodiments, the fiber
web may have at least one modified surface. In some embodiments,
the fiber web comprises a plurality of fibers wherein at least a
portion of the fibers comprise a modified surface. The material
used to modify at least one surface of the fiber web and/or fibers
may be applied on any suitable portion of the fiber web. In some
embodiments, the material may be applied such that one or more
surfaces of the fiber web are modified without substantially
modifying the interior of the fiber web. In some instances, a
single surface of the fiber web may be modified. For example, the
upstream surface of the fiber web may be coated. In other
instances, more than one surface of the fiber web may be coated
(e.g., the upstream and downstream surfaces). In other embodiments,
at least a portion of the interior of the fiber web may be modified
along with at least one surface of the fiber web. In some
embodiments, the entire fiber web is modified with the
material.
In general, any suitable method for modifying the surface chemistry
of at least one surface of the fiber web and/or the plurality of
fibers may be used. In some embodiments, the surface chemistry of
the fiber web and/or the plurality of fibers may be modified by
coating at least a portion of the surface, using melt-additives,
and/or altering the roughness of the surface.
In some embodiments, the surface modification may be a coating. In
certain embodiments, a coating process involves introducing resin
or a material (e.g., hydrophobic material, hydrophilic material,
lipophilic material, lipophobic material) dispersed in a solvent or
solvent mixture into a pre-formed fiber layer (e.g., a pre-formed
fiber web formed by a meltblown process). Non-limiting examples of
coating methods include the use of chemical vapor deposition, a
slot die coater, gravure coating, screen coating, size press
coating (e.g., a two roll-type or a metering blade type size press
coater), film press coating, blade coating, roll-blade coating, air
knife coating, roll coating, foam application, reverse roll
coating, bar coating, curtain coating, champlex coating, brush
coating, Bill-blade coating, short dwell-blade coating, lip
coating, gate roll coating, gate roll size press coating,
laboratory size press coating, melt coating, dip coating, knife
roll coating, spin coating, spray coating, gapped roll coating,
roll transfer coating, padding saturant coating, and saturation
impregnation. Other coating methods are also possible. In some
embodiments, the hydrophilic, hydrophobic, lipophilic, and/or
lipophobic material may be applied to the fiber web using a
non-compressive coating technique. The non-compressive coating
technique may coat the fiber web, while not substantially
decreasing the thickness of the web. In other embodiments, the
resin may be applied to the fiber web using a compressive coating
technique.
In one set of embodiments, a surface described herein is modified
using chemical vapor deposition. In chemical vapor deposition, the
fiber web is exposed to gaseous reactants from gas or liquid vapor
that are deposited onto the fiber web under high energy level
excitation such as thermal, microwave, UV, electron beam or plasma.
Optionally, a carrier gas such as oxygen, helium, argon and/or
nitrogen may be used.
Other vapor deposition methods include atmospheric pressure
chemical vapor deposition (APCVD), low pressure chemical vapor
deposition (LPCVD), metal-organic chemical vapor deposition
(MOCVD), plasma assisted chemical vapor deposition (PACVD) or
plasma enhanced chemical vapor deposition (PECVD), laser chemical
vapor deposition (LCVD), photochemical vapor deposition (PCVD),
chemical vapor infiltration (CVI) and chemical beam epitaxy
(CBE).
In physical vapor deposition (PVD) thin films are deposited by the
condensation of a vaporized form of the desired film material onto
substrate. This method involves physical processes such as
high-temperature vacuum evaporation with subsequent condensation,
or plasma sputter bombardment rather than a chemical reaction.
After applying the coating to the fiber web, the coating may be
dried by any suitable method. Non-limiting examples of drying
methods include the use of a photo dryer, infrared dryer, hot air
oven steam-heated cylinder, or any suitable type of dryer familiar
to those of ordinary skill in the art.
In some embodiments, at least a portion of the fibers of the fiber
web may be coated without substantially blocking the pores of the
fiber web. In some instances, substantially all of the fibers may
be coated without substantially blocking the pores. In some
embodiments, the fiber web may be coated with a relatively high
weight percentage of resin or material without blocking the pores
of the fiber web using the methods described herein (e.g., by
dissolving and/or suspending one or more material in a solvent to
form the resin).
In some embodiments, the surface may be modified using melt
additives. Melt-additives are functional chemicals that are added
to thermoplastics fibers during an extrusion process that may
render different physical and chemical properties at the surface
from those of the thermoplastic itself after formation.
In some embodiments, the material may undergo a chemical reaction
(e.g., polymerization) after being applied to the fiber web. For
example, a surface of the fiber web may be coated with one or more
monomers that can be polymerized after coating. In another example,
a surface of the fiber web may include monomers, as a result of the
melt additive, that are polymerized after formation of the fiber
web. In some such embodiments, an in-line polymerization may be
used. In-line polymerization (e.g., in-line ultraviolet
polymerization) is a process to cure a monomer or liquid polymer
solution onto a substrate under conditions sufficient to induce
polymerization (e.g., under UV irradiation).
In general, any suitable material may be used to alter the surface
chemistry, and accordingly the lipophilicity, of the fiber web. In
some embodiments, the material may be charged. In some such
embodiments, as described in more detail herein, the surface charge
of the fiber web may further facilitate coalescence and/or increase
the oil carry over. For instance, in certain embodiments, a fiber
web having a lipophilic modified surface may have a decreased oil
carry over and/or produce larger coalesced droplets than a fiber
web having a non-modified surface.
In general, the net charge of the modified surface may be negative,
positive, or neutral. In some instances, the modified surface may
comprise a negatively charged material and/or a positively charged
material. In some embodiments, the surface may be modified with an
electrostatically neutral material. Non-limiting examples of
materials that may be used to modify the surface include
polyelectrolytes (e.g., anionic, cationic), oligomers, polymers
(e.g., fluorinated polymers, perfluoroalkyl ethyl methacrylate,
polycaprolactone, poly [bis(trifluoroethoxy)phosphazene], small
molecules (e.g., carboxylate containing monomers, amine containing
monomers, polyol), ionic liquids, monomer precursors, and gases,
and combinations thereof.
In embodiments in which fluorinated polymers are included, the
polymer may include a species having the formula
--C.sub.nF.sub.2n+1 or --C.sub.nF.sub.m, where n is an integer
greater than 1, and m is an integer greater than 1 (e.g.,
--C.sub.6F.sub.13). In some embodiments, anionic polyelectrolytes
may be used to modify the surface of the fiber web. For example,
one or more anionic polyelectrolytes may be spray or dip coated
onto at least one surface of the fiber web. In some embodiments,
cationic polyelectrolytes may be used to modify the surface of the
fiber web. In some embodiments, silicone (or derivatives thereof)
may be used to modify the surface of the fiber web. For example, in
certain embodiments, at least a surface of the fiber web may be
treated or coated with polydimethylsiloxane. In certain
embodiments, the surface of the fiber web may be silylated (e.g., a
substituted silyl group may be incorporated onto at least a surface
of the fiber web).
In certain embodiments, a filler material (e.g., an organic filler
material, and inorganic filler material) may be added to the fiber
web to modify the surface and/or oil repellency level of the fiber
web. In some embodiments, small molecules (e.g., monomers, polyol)
may be used to modify the oil repellency level of the fiber webIn
certain embodiments, small molecules may be used as melt-additives.
In another example, small molecules may be deposited on at least
one surface of the fiber web via coating (e.g., chemical vapor
deposition). Regardless of the modification method, the small
molecules on a surface of the fiber web may be polymerized after
deposition in some embodiments.
In certain embodiments, the small molecules, such as monobasic
carboxylic acids and/or unsaturated dicarboxylic (dibasic) acids,
may be used to modify at least one surface of the fiber web. In
certain embodiments, the small molecules may be amine containing
small molecules. The amine containing small molecules may be
primary, secondary, or tertiary amines. In some such cases, the
amine containing small molecule may be a monomer. In some
embodiments, the small molecule may be an inorganic or organic
hydrophobic molecule. Non-limiting examples include hydrocarbons
(e.g., CH.sub.4, C.sub.2H.sub.2, C.sub.2H.sub.4, C.sub.6H.sub.6),
fluorocarbons (e.g., CF.sub.4, C.sub.2F.sub.4, C.sub.3F.sub.6,
C.sub.3F.sub.8, C.sub.4H.sub.8, C.sub.5H.sub.12, C.sub.6F.sub.6,
C.sub.6F.sub.13, or other fluorocarbons having the formula
--C.sub.nF.sub.2n+1 or --C.sub.nF.sub.m, where n is an integer
greater than 1, and m is an integer greater than 1), silanes (e.g.,
SiH.sub.4, Si.sub.2H.sub.6, Si.sub.3H.sub.8, Si.sub.4H.sub.10),
organosilanes (e.g., methylsilane, dimethylsilane, triethylsilane),
and siloxanes (e.g., dimethylsiloxane, hexamethyldisiloxane). In
certain embodiments, suitable hydrocarbons for modifying a surface
of the fiber web may have the formula C.sub.xH.sub.y, where x is an
integer from 1 to 10 and y is an integer from 2 to 22. In certain
embodiments, suitable silanes for modifying a surface of the fiber
web may have the formula Si.sub.nH.sub.2n+2 where any hydrogen may
be substituted for a halogen (e.g., Cl , F, Br, I), where n is an
integer from 1 to 10.
As used herein, "small molecules" refers to molecules, whether
naturally-occurring or artificially created (e.g., via chemical
synthesis) that have a relatively low molecular weight. Typically,
a small molecule is an organic compound (i.e., it contains carbon).
The small organic molecule may contain multiple carbon-carbon
bonds, stereocenters, and other functional groups (e.g., amines,
hydroxyl, carbonyls, and heterocyclic rings, etc.). In certain
embodiments, the molecular weight of a small molecule is at most
about 1,000 g/mol, at most about 900 g/mol, at most about 800
g/mol, at most about 700 g/mol, at most about 600 g/mol, at most
about 500 g/mol, at most about 400 g/mol, at most about 300 g/mol,
at most about 200 g/mol, or at most about 100 g/mol. In certain
embodiments, the molecular weight of a small molecule is at least
about 100 g/mol, at least about 200 g/mol, at least about 300
g/mol, at least about 400 g/mol, at least about 500 g/mol, at least
about 600 g/mol, at least about 700 g/mol, at least about 800
g/mol, or at least about 900 g/mol, or at least about 1,000 g/mol.
Combinations of the above ranges (e.g., at least about 200 g/mol
and at most about 500 g/mol) are also possible.
In some embodiments, polymers may be used to modify at least one
surface of the fiber web. For example, one or more polymer may be
applied to at least a portion of a surface of the fiber web via a
coating technique. In certain embodiments, the polymer may be
formed from monobasic carboxylic acids and/or unsaturated
dicarboxylic (dibasic) acids. In certain embodiments, the polymer
may be a graft copolymer and may be formed by grafting polymers or
oligomers to polymers in the fibers and/or fiber web (e.g., resin
polymer). The graft polymer or oligomer may comprise carboxyl
moieties that can be used to form a chemical bond between the graft
and polymers in the fibers and/or fiber web. Non-limiting examples
of polymers in the fibers and/or fiber web that can be used to form
a graft copolymer include polyethylene, polypropylene,
polycarbonate, polyvinyl chloride, polytetrafluoroethylene,
polystyrene, cellulose, polyethylene terephthalate, polybutylene
terephthalate, and nylon, and combinations thereof. Graft
polymerization can be initiated through chemical and/or
radiochemical (e.g., electron beam, plasma, corona discharge,
UV-irradiation) methods. In some embodiments, the polymer may be a
polymer having a repeat unit that comprises an amine (e.g.,
polyallylamine, polyethyleneimine, polyoxazoline). In certain
embodiments, the polymer may be a polyol.
In some embodiments, a gas may be used to modify at least one
surface of the fiber web. In some such cases, the molecules in the
gas may react with material (e.g., fibers, resin, additives) on the
surface of the fiber web to form functional groups, such as charged
moieties, and/or to increase the oxygen content on the surface of
the fiber web. The weight percent of the material used to modify at
least one surface of the fiber web may be greater than or equal to
about 0.0001 wt %, greater than or equal to about 0.0005 wt %,
greater than or equal to about 0.001 wt %, greater than or equal to
about 0.005 wt %, greater than or equal to about 0.01 wt %, greater
than or equal to about 0.05 wt %, greater than or equal to about
0.1 wt %, greater than or equal to about 0.5 wt %, greater than or
equal to about 1 wt %, greater than or equal to about 2 wt %, or
greater than or equal to about 3 wt % of the fiber web. In some
cases, the weight percentage of the material used to modify at
least one surface of the fiber web may be less than or equal to
about 4 wt %, less than or equal to about 3 wt %, less than or
equal to about 1 wt %, less than or equal to about 0.5 wt %, less
than or equal to about 0.1 wt %, less than or equal to about 0.05
wt %, less than or equal to about 0.01 wt %, or less than or equal
to about 0.005 wt % of the fiber web. Combinations of the
above-referenced ranges are also possible (e.g., a weight
percentage of material of greater than or equal to about 0.0001 wt
% and less than about 4 wt %, or greater than or equal to about
0.01 wt % and less than about 0.5 wt %). Other ranges are also
possible. The weight percentage of material in the fiber web is
based on the dry solids of the fiber web and can be determined by
weighing the fiber web before and after the material is
applied.
The fiber web, as described herein, may have certain structural
characteristics such as basis weight. For instance, in some
embodiments, the fiber web may have a basis weight of greater than
or equal to about 1 g/m.sup.2, greater than or equal to about 5
g/m.sup.2, greater than or equal to about 10 g/m.sup.2, greater
than or equal to about 20 g/m.sup.2, greater than or equal to about
27 g/m.sup.2, greater than or equal to about 30 g/m.sup.2, greater
than or equal to about 40 g/m.sup.2, greater than or equal to about
50 g/m.sup.2, greater than or equal to about 100 g/m.sup.2, greater
than or equal to about 150 g/m.sup.2, greater than or equal to
about 200 g/m.sup.2, greater than or equal to about 250 g/m.sup.2,
greater than or equal to about 270 g/m.sup.2, greater than or equal
to about 300 g/m.sup.2, greater than or equal to about 350
g/m.sup.2, greater than or equal to about 400 g/m.sup.2, or greater
than or equal to about 450 g/m.sup.2. In certain embodiments, the
fiber web may have basis weight of less than or equal to about 500
g/m.sup.2, less than or equal to about 450 g/m.sup.2, less than or
equal to about 400 g/m.sup.2, less than or equal to about 350
g/m.sup.2, less than or equal to about 300 g/m.sup.2, less than or
equal to about 270 g/m.sup.2, less than or equal to about 250
g/m.sup.2, less than or equal to about 200 g/m.sup.2, less than or
equal to about 150 g/m.sup.2, less than or equal to about 100
g/m.sup.2, less than or equal to about 50 g/m.sup.2, less than or
equal to about 40 g/m.sup.2, less than or equal to about 30
g/m.sup.2, less than or equal to about 27 g/m.sup.2, less than or
equal to about 25 g/m.sup.2, less than or equal to about 20
g/m.sup.2, less than or equal to about 10 g/m.sup.2, or less than
or equal to about 5 g/m.sup.2. Combinations of the above-referenced
ranges are also possible (e.g., greater than or equal to about 1
g/m.sup.2 and less than or equal to about 500 g/m.sup.2, greater
than or equal to about 20 g/m.sup.2 and less than or equal to about
500 g/m.sup.2, greater than or equal to about 27 g/m.sup.2 and less
than or equal to about 270 g/m.sup.2). Other values of basis weight
are also possible. The basis weight may be determined according to
the standard ASTM D-846.
The mean flow pore size may be selected as desired. With respect to
the mean flow pore size of a fiber web, whether the fiber web
includes perforations or does not include any perforations, the
mean flow pore size as used herein is measured in an area of the
fiber web that does not include any perforations. In some
embodiments, the fiber web may have a mean flow pore size of
greater than or equal to about 1 microns, greater than or equal to
about 3 microns, greater than or equal to about 4 microns, greater
than or equal to about 5 microns, greater than or equal to about 6
microns, greater than or equal to about 7 microns, or greater than
or equal to about 9 microns. In some instances, the fiber web may
have a mean flow pore size of less than or equal to about 10
microns, less than or equal to about 8 microns, less than or equal
to about 6 microns, less than or equal to about 5 microns, less
than or equal to about 4 microns, or less than or equal to about 2
microns. Combinations of the above-referenced ranges are also
possible (e.g., greater than or equal to about 3 microns and less
than or equal to about 6 microns).
Other values of mean flow pore size are also possible. The mean
flow pore size may be determined according to the standard ASTM
E1294 (2008) (M.F.P.).
The thickness of the fiber web may be selected as desired. For
instance, in some embodiments, the fiber web may have a thickness
of greater than or equal to about 0.1 mm, greater than or equal to
about 0.2 mm, greater than or equal to about 0.3 mm, greater than
or equal to about 0.4 mm, greater than or equal to about 0.5 mm,
greater than or equal to about 1.0 mm, or greater than or equal to
about 1.5 mm. In some instances, the fiber web may have a thickness
of less than or equal to about 2.0 mm, less than or equal to about
1.2 mm, less than or equal to about 0.5 mm, less than or equal to
about 0.4 mm, less than or equal to about 0.3 mm, or less than or
equal to about 0.2 mm. Combinations of the above-referenced ranges
are also possible (e.g., a thickness of greater than or equal to
about 0.2 mm and less than or equal to about 0.5 mm). Other values
of thickness are also possible. The thickness may be determined
according to the standard TAPPI T411.
The fiber web (or filter media) described herein may be used for
the filtration of various particle sizes. In a typical test for
measuring efficiency of a layer or the entire media (e.g.,
according to the standard ISO 19438), particle counts (particles
per milliliter) at the particle size, x, selected (e.g., where x is
1, 3, 4, 5, 7, 10, 15, 20, 25, or 30 microns) upstream and
downstream of the layer or media can be taken at ten points equally
divided over the time of the test. Generally, a particle size of x
means that x micron or greater particles will be captured by the
layer or media. The average of upstream and downstream particle
counts can be taken at the selected particle size. From the average
particle count upstream (injected --C.sub.0) and the average
particle count downstream (passed thru --C) the filtration
efficiency test value for the particle size selected can be
determined by the relationship [(1[C/C.sub.0])*100%]. As described
herein, efficiency can be measured according to standard ISO 19348.
A similar protocol can be used for measuring initial efficiency,
which refers to the efficiency measurements of the media at 4
minutes after running the test. Unless otherwise indicated,
efficiency and initial efficiency measurements described herein
refer to values where x 13 4 microns.
The fiber web (or filter media) may have a relatively high initial
efficiency. The initial efficiency of the fiber web may be greater
than or equal to about 1%, greater than or equal to about 5%,
greater than or equal to about 10%, greater than or equal to about
20%, greater than or equal to about 30%, greater than or equal to
about 40%, greater than or equal to about 50%, greater than or
equal to about 60%, greater than or equal to about 70%, greater
than or equal to about 80%, greater than or equal to about 90%,
greater than or equal to about 95%, greater than or equal to about
96%, greater than or equal to about 97%, greater than or equal to
about 98%, greater than or equal to about 99%, or greater than or
equal to about 99.9%. In some instances, the initial efficiency of
the fiber web may be less than or equal to about 99.99%, less than
or equal to about 98%, less than or equal to about 97%, less than
or equal to about 96%, less than or equal to about 90%, less than
or equal to about 80%, less than or equal to about 70%, less than
or equal to about 60%, less than or equal to about 50%, less than
or equal to about 40%, less than or equal to about 30%, less than
or equal to about 20%, less than or equal to about 10%, or less
than or equal to about 5%. Combinations of the above-referenced
ranges are also possible (e.g., greater than or equal to about 1%
and less than or equal to about 99.99%, greater than or equal to
about 80% and less than or equal to about 99.99%). Other values of
the initial efficiency of the fiber web are also possible.
The air permeability of the fiber web described herein can vary. In
some embodiments, the permeability of the fiber web may be, for
example, greater than or equal to about 5 L/m.sup.2s, greater than
or equal to about 10 L/m.sup.2s, greater than or equal to about 15
L/m.sup.2s, greater than or equal to about 25 L/m.sup.2s, greater
than or equal to about 50 L/m.sup.2s, greater than or equal to
about 100 L/m.sup.2s, greater than or equal to about 150
L/m.sup.2s, greater than or equal to about 200 L/m.sup.2s, greater
than or equal to about 250 L/m.sup.2s, greater than or equal to
about 300 L/m.sup.2s, greater than or equal to about 500
L/m.sup.2s, greater than or equal to about 1000 L/m.sup.2s, greater
than or equal to about 1500 L/m.sup.2s, greater than or equal to
about 1700 L/m.sup.2s, greater than or equal to about 2000
L/m.sup.2s, or greater than or equal to about 2500 L/m.sup.2s. In
some instances, the air permeability may be, for example, less than
or equal to about 3000 L/m.sup.2s, less than or equal to about 2500
L/m.sup.2s, less than or equal to about 2000 L/m.sup.2s, less than
or equal to about 1700 L/m.sup.2s, less than or equal to about 1500
L/m.sup.2s, less than or equal to about 1000 L/m.sup.2s, less than
or equal to about 500 L/m.sup.2s, less than or equal to about 300
L/m.sup.2s, less than or equal to about 250 L/m.sup.2s, less than
or equal to about 200 L/m.sup.2s, less than or equal to about 150
L/m.sup.2s, less than or equal to about 100 L/m.sup.2s, less than
or equal to about 50 L/m.sup.2s, less than or equal to about 25
L/m.sup.2s, less than or equal to about 20 L/m.sup.2s, less than or
equal to about 15 L/m.sup.2s, or less than or equal to about 10
L/m.sup.2s. Combinations of the above-referenced ranges are also
possible (greater than or equal to about 5 L/m.sup.2s and less than
or equal to about 3000 L/m.sup.2s, greater than or equal to about
15 L/m.sup.2s and less than or equal to about 1700 L/m.sup.2s).
Other ranges of air permeability are also possible. As determined
herein, the air permeability is measured according to standard
TAPPI T251 (wherein the flow is 10,000 L/m.sup.2/s on 20 cm.sup.2
area). The permeability of a fiber web is an inverse function of
flow resistance and can be measured with a Frazier Permeability
Tester. The Frazier Permeability Tester measures the volume of air
per unit of time that passes through a unit area of media at a
fixed differential pressure across the media.
The overall pressure drop of the fiber web may be selected as
desired. For instance, in some embodiments, the fiber web may have
an overall pressure drop of less than or equal to about 1700 Pa,
less than or equal to about 1500 Pa, less than or equal to about
1000 Pa, less than or equal to about 700 Pa, less than or equal to
about 500 Pa, less than or equal to about 250 Pa, less than or
equal to about 100 Pa, less than or equal to about 50 Pa, less than
or equal to about 25 Pa, less than or equal to about 10 Pa, or less
than or equal to about 5 Pa. In certain embodiments, the fiber web
may have an overall pressure drop of greater than or equal to about
3 Pa, greater than or equal to about 5 Pa, greater than or equal to
about 10 Pa, greater than or equal to about 25 Pa, greater than or
equal to about 50 Pa, greater than or equal to about 100 Pa,
greater than or equal to about 250 Pa, greater than or equal to
about 500 Pa, greater than or equal to about 700 Pa, greater than
or equal to about 1000 Pa, or greater than or equal to about 1500
Pa. Combinations of the above-referenced ranges are also possible
(e.g., greater than or equal to about 3 Pa and less than or equal
to about 1700 Pa, greater than or equal to about 10 Pa and less
than or equal to about 700 Pa). Other values of pressure drop are
also possible. The pressure drop may be measured using the TAPPI
T251 standard.
As described herein, in some embodiments a filter element comprises
a core. In some embodiments, the core may comprise a plastic and/or
metallic net, and/or a mesh. Non-limiting examples of suitable
meshes include polymer meshes (e.g., comprising fluoropolymers,
polyamides, polyolefins, polyesters, polysulfones, polyvinyls, or
combinations thereof) and metal meshes (e.g., comprising stainless
steel). In some embodiments, the core comprises a metal sheet
(e.g., stainless steel) which may or may not be perforated. In
certain embodiments, the core is fibrous. For example, in some
embodiments, the core comprises a plurality of synthetic fibers. In
some cases, the core may have a specific weight percentage of
synthetic fibers.
For instance, in some embodiments, the weight percentage of
synthetic fibers in the core may be greater than or equal to about
0%, greater than or equal to about 10%, greater than or equal to
about 20%, greater than or equal to about 30%, greater than or
equal to about 40%, greater than or equal to about 55%, greater
than or equal to about 70%, greater than or equal to about 75%,
greater than or equal to about 80%, or greater than or equal to
about 90%. In some instances, the weight percentage of synthetic
fibers in the core may be less than or equal to about 100%, less
than or equal to about 85%, less than or equal to about 75%, less
than or equal to about 65%, less than or equal to about 55%, less
than or equal to about 45%, less than or equal to about 35%, less
than or equal to about 25%, or less than or equal to about 15%.
Combinations of the above-referenced ranges are also possible
(e.g., greater than or equal to about 0% and less than or equal to
about 100%). In some embodiments, 100% of the fibers in the core
are synthetic fibers. Other values of weight percentage of the
synthetic fibers in the core are also possible.
In some embodiments, the fibers (e.g., synthetic fibers) in the
core may have an average diameter of greater than or equal to about
0.5 microns, greater than or equal to about 0.6 microns, greater
than or equal to about 1 micron, greater than or equal to about 2
microns, greater than or equal to about 3 microns, greater than or
equal to about 4 microns, greater than or equal to about 6 microns,
greater than or equal to about 8 microns, greater than or equal to
about 10 microns, greater than or equal to about 15 microns,
greater than or equal to about 20 microns, greater than or equal to
about 30 microns, or greater than or equal to about 40 microns. In
some instances, the fibers in the core may have an average diameter
of less than or equal to about 50 microns, less than or equal to
about 40 microns, less than or equal to about 30 microns, less than
or equal to about 20 microns, less than or equal to about 15
microns, less than or equal to about 10 microns, less than or equal
to about 8 microns, less than or equal to about 6 microns, less
than or equal to about 4 microns, less than or equal to about 3
microns, less than or equal to about 2 microns, less than or equal
to about 1 micron, or less than or equal to about 0.6 microns.
Combinations of the above-referenced ranges are also possible
(e.g., greater than or equal to about 0.5 micron and less than or
equal to about 50 microns, greater than or equal to about 0.6
microns and less than or equal to about 20 microns). Other values
of average fiber diameter are also possible.
In some embodiments, fibers (e.g., synthetic fibers) in the core
may have an average length of greater than or equal to about 1 mm,
greater than or equal to about 2 mm, greater than or equal to about
3 mm, greater than or equal to about 4 mm, greater than or equal to
about 6 mm, greater than or equal to about 8 mm, greater than or
equal to about 10 mm, greater than or equal to about 12 mm, greater
than or equal to about 15 mm, greater than or equal to about 20 mm,
greater than or equal to about 25 mm, greater than or equal to 30
mm, or greater than or equal to 40 mm. In some instances, the
fibers may have an average length of less than or equal to about 50
mm, less than or equal to about 40 mm, less than or equal to about
30 mm, less than or equal to about 25 mm, less than or equal to
about 20 mm, less than or equal to about 15 mm, less than or equal
to about 12 mm, less than or equal to about 10 mm, less than or
equal to about 8 mm less than or equal to about 7 mm, less than or
equal to about 5 mm, less than or equal to about 3 mm, less than or
equal to about 2 mm, or less than or equal to about 1.5 mm.
Combinations of the above-referenced ranges are also possible
(e.g., greater than or equal to about 1 mm and less than or equal
to about 50 mm, greater than or equal to about 1 mm and less than
or equal to about 15 mm, greater than or equal to about 1.5 mm and
less than or equal to about 30 mm,). Other values of average fiber
length are also possible.
The core, as described herein, may have certain structural
characteristics, such as basis weight, and thickness. For instance,
in some embodiments, the core may have a basis weight of greater
than or equal to about 3 g/m.sup.2, greater than or equal to about
10 g/m.sup.2, greater than or equal to about 22 g/m.sup.2, greater
than or equal to about 25 g/m.sup.2, greater than or equal to about
30 g/m.sup.2, greater than or equal to about 33 g/m.sup.2, greater
than or equal to about 40 g/m.sup.2, greater than or equal to about
50 g/m.sup.2, greater than or equal to about 60 g/m.sup.2, greater
than or equal to about 70 g/m.sup.2, greater than or equal to about
80 g/m.sup.2, greater than or equal to about 100 g/m.sup.2, greater
than or equal to about 200 g/m.sup.2, greater than or equal to
about 300 g/m.sup.2, or greater than or equal to about 400
g/m.sup.2. In some instances, the core may have a basis weight of
less than or equal to about 500 g/m.sup.2, less than or equal to
about 400 g/m.sup.2, less than or equal to about 300 g/m.sup.2,
less than or equal to about 200 g/m.sup.2, less than or equal to
about 100 g/m.sup.2, less than or equal to about 90 g/m.sup.2, less
than or equal to about 80 g/m.sup.2, less than or equal to about 70
g/m.sup.2, less than or equal to about 60 g/m.sup.2, less than or
equal to about 50 g/m.sup.2, less than or equal to about 40
g/m.sup.2, less than or equal to about 33 g/m.sup.2, less than or
equal to about 30 g/m.sup.2, or less than or equal to about 25
g/m.sup.2. Combinations of the above-referenced ranges are also
possible (e.g., a basis weight of greater than or equal to about 22
g/m.sup.2 and less than or equal to about 90 g/m.sup.2, a basis
weight of greater than or equal to about 33 g/m.sup.2 and less than
or equal to about 70 g/m.sup.2, a basis weight of greater than or
equal to about 3 g/m.sup.2 and less than or equal to about 500
g/m.sup.2). Other values of basis weight are also possible. The
basis weight may be determined according to the standard ASTM
D-846.
The thickness of the core may be selected as desired. For instance,
in some embodiments, the core may have a thickness of greater than
or equal to about 0.01 mm, greater than or equal to about 0.1 mm,
greater than or equal to about 0.2 mm, greater than or equal to
about 0.3 mm, greater than or equal to about 0.4 mm, greater than
or equal to about 0.5 mm, greater than or equal to about 1.0 mm,
greater than or equal to about 1.5 mm, greater than or equal to
about 2 mm, greater than or equal to about 3 mm, or greater than or
equal to about 4 mm. In some instances, the core may have a
thickness of less than or equal to about 5 mm, less than or equal
to about 4 mm, less than or equal to about 3 mm, less than or equal
to about 2 mm, less than or equal to about 1.2 mm, less than or
equal to about 0.5 mm, less than or equal to about 0.4 mm, less
than or equal to about 0.3 mm, less than or equal to about 0.2 mm,
or less than or equal to about 0.1 mm. Combinations of the
above-referenced ranges are also possible (e.g., a thickness of
greater than or equal to about 0.01 mm and less than or equal to
about 5 mm, a thickness of greater than or equal to about 0.1 mm
and less than or equal to about 2 mm). Other values of thickness
are also possible. The thickness may be determined according to the
standard TAPPI T411.
As described herein, in some embodiments a filter media may include
one or more support layers. The support layer(s) may include a
plurality of fibers. In general, a number of different materials
can be used to form the fibers as described below. In some
embodiments, the fibers are made from cellulose. Examples of
cellulose fibers are provided above. In certain embodiments, the
support layer may include synthetic fibers, as described above. In
some cases, the support layer may be a perforated film comprising
bio-derived and/or metal materials.
In some cases, the support layer may have a specific weight
percentage of synthetic fibers. For instance, in some embodiments,
the weight percentage of synthetic fibers in the support layer may
be greater than or equal to about 0%, greater than or equal to
about 10%, greater than or equal to about 20%, greater than or
equal to about 30%, greater than or equal to about 40%, greater
than or equal to about 55%, greater than or equal to about 70%,
greater than or equal to about 75%, greater than or equal to about
80%, or greater than or equal to about 90%. In some instances, the
weight percentage of synthetic fibers in the support layer may be
less than or equal to about 100%, less than or equal to about 85%,
less than or equal to about 75%, less than or equal to about 65%,
less than or equal to about 55%, less than or equal to about 45%,
less than or equal to about 35%, less than or equal to about 25%,
or less than or equal to about 15%. Combinations of the
above-referenced ranges are also possible (e.g., greater than or
equal to about 0% and less than or equal to about 100%). In some
embodiments, 100% of the fibers in the support layer are synthetic
fibers. Other values of weight percentage of the synthetic fibers
in the support layer are also possible.
The support layer may include one or more of glass fibers,
cellulose fibers, and/or bicomponent fibers, as described above in
the context of the fiber web. For instance, in some embodiments,
the weight percentage of each of glass fibers, binder fibers,
and/or cellulose fibers in the support layer may independently be
greater than or equal to about 0%, greater than or equal to about
0.1%, greater than or equal to about 1%, greater than or equal to
about 2%, greater than or equal to about 5%, greater than or equal
to about 10%, greater than or equal to about 15%, greater than or
equal to about 20%, greater than or equal to about 30%, greater
than or equal to about 40%, greater than or equal to about 50%,
greater than or equal to about 60%, greater than or equal to about
70%, greater than or equal to about 80%, or greater than or equal
to about 90%. In some instances, the weight percentage of each of
the glass fibers, binder fibers, and/or cellulose fibers in the
support layer may independently be less than or equal to about
100%, less than or equal to about 90%, less than or equal to about
80%, less than or equal to about 70%, less than or equal to about
60%, less than or equal to about 50%, less than or equal to about
40%, less than or equal to about 30%, less than or equal to about
20%, less than or equal to about 15%, less than or equal to about
10%, less than or equal to about 5%, less than or equal to about
2%, less than or equal to about 0.5%, or less than or equal to
about 0.1%. Combinations of the above-referenced ranges are also
possible (e.g., greater than or equal to about 0% and less than or
equal to about 20%). Other values of weight percentages of the
fibers in the support layer are also possible. Examples of glass
fibers, and binder fibers are provided in more detail herein.
In some embodiments, the fibers in the support layer may have an
average diameter of greater than or equal to about 0.5 microns,
greater than or equal to about 0.6 microns, greater than or equal
to about 1 micron, greater than or equal to about 2 microns,
greater than or equal to about 3 microns, greater than or equal to
about 4 microns, greater than or equal to about 6 microns, greater
than or equal to about 8 microns, greater than or equal to about 10
microns, greater than or equal to about 15 microns, greater than or
equal to about 20 microns, greater than or equal to about 30
microns, or greater than or equal to about 40 microns. In some
instances, the fibers in the support layer may have an average
diameter of less than or equal to about 50 microns, less than or
equal to about 40 microns, less than or equal to about 30 microns,
less than or equal to about 20 microns, less than or equal to about
15 microns, less than or equal to about 10 microns, less than or
equal to about 8 microns, less than or equal to about 6 microns,
less than or equal to about 4 microns, less than or equal to about
3 microns, less than or equal to about 2 microns, less than or
equal to about 1 micron, or less than or equal to about 0.6
microns. Combinations of the above-referenced ranges are also
possible (e.g., greater than or equal to about 0.5 micron and less
than or equal to about 50 microns, greater than or equal to about
0.6 microns and less than or equal to about 20 microns). Other
values of average fiber diameter are also possible.
In some embodiments, fibers in the support layer may have an
average length of greater than or equal to about 1 mm, greater than
or equal to about 2 mm, greater than or equal to about 3 mm,
greater than or equal to about 4 mm, greater than or equal to about
6 mm, greater than or equal to about 8 mm, greater than or equal to
about 10 mm, greater than or equal to about 12 mm, greater than or
equal to about 15 mm, greater than or equal to about 20 mm, greater
than or equal to about 25 mm, greater than or equal to 30 mm, or
greater than or equal to 40 mm. In some instances, the fibers may
have an average length of less than or equal to about 50 mm, less
than or equal to about 40 mm, less than or equal to about 30 mm,
less than or equal to about 25 mm, less than or equal to about 20
mm, less than or equal to about 15 mm, less than or equal to about
12 mm, less than or equal to about 10 mm, less than or equal to
about 8 mm less than or equal to about 7 mm, less than or equal to
about 5 mm, less than or equal to about 3 mm, less than or equal to
about 2 mm, or less than or equal to about 1.5 mm. Combinations of
the above-referenced ranges are also possible (e.g., greater than
or equal to about 1 mm and less than or equal to about 50 mm,
greater than or equal to about 1 mm and less than or equal to about
15 mm, greater than or equal to about 1.5 mm and less than or equal
to about 30 mm,). Other values of average fiber length are also
possible.
The support layer, as described herein, may have certain structural
characteristics, such as basis weight, and thickness. For instance,
in some embodiments, the support layer may have a basis weight of
greater than or equal to about 3 g/m.sup.2, greater than or equal
to about 10 g/m.sup.2, greater than or equal to about 22 g/m.sup.2,
greater than or equal to about 25 g/m.sup.2, greater than or equal
to about 30 g/m.sup.2, greater than or equal to about 33 g/m.sup.2,
greater than or equal to about 40 g/m.sup.2, greater than or equal
to about 50 g/m.sup.2, greater than or equal to about 60 g/m.sup.2,
greater than or equal to about 70 g/m.sup.2, greater than or equal
to about 80 g/m.sup.2, greater than or equal to about 100
g/m.sup.2, greater than or equal to about 200 g/m.sup.2, greater
than or equal to about 300 g/m.sup.2, or greater than or equal to
about 400 g/m.sup.2. In some instances, the support layer may have
a basis weight of less than or equal to about 500 g/m.sup.2, less
than or equal to about 400 g/m.sup.2, less than or equal to about
300 g/m.sup.2, less than or equal to about 200 g/m.sup.2, less than
or equal to about 100 g/m.sup.2, less than or equal to about 90
g/m.sup.2, less than or equal to about 80 g/m.sup.2, less than or
equal to about 70 g/m.sup.2, less than or equal to about 60
g/m.sup.2, less than or equal to about 50 g/m.sup.2, less than or
equal to about 40 g/m.sup.2, less than or equal to about 33
g/m.sup.2, less than or equal to about 30 g/m.sup.2, or less than
or equal to about 25 g/m.sup.2. Combinations of the
above-referenced ranges are also possible (e.g., a basis weight of
greater than or equal to about 22 g/m.sup.2 and less than or equal
to about 90 g/m.sup.2, a basis weight of greater than or equal to
about 33 g/m.sup.2 and less than or equal to about 70 g/m.sup.2, a
basis weight of greater than or equal to about 3 g/m.sup.2 and less
than or equal to about 500 g/m.sup.2). Other values of basis weight
are also possible. The basis weight may be determined according to
the standard ASTM D-846.
The thickness of the support layer may be selected as desired. For
instance, in some embodiments, the support layer may have a
thickness of greater than or equal to about 0.01 mm, greater than
or equal to about 0.1 mm, greater than or equal to about 0.2 mm,
greater than or equal to about 0.3 mm, greater than or equal to
about 0.4 mm, greater than or equal to about 0.5 mm, greater than
or equal to about 1.0 mm, greater than or equal to about 1.5 mm,
greater than or equal to about 2 mm, greater than or equal to about
3 mm, or greater than or equal to about 4 mm. In some instances,
the support layer may have a thickness of less than or equal to
about 5 mm, less than or equal to about 4 mm, less than or equal to
about 3 mm, less than or equal to about 2 mm, less than or equal to
about 1.2 mm, less than or equal to about 0.5 mm, less than or
equal to about 0.4 mm, less than or equal to about 0.3 mm, less
than or equal to about 0.2 mm, or less than or equal to about 0.1
mm. Combinations of the above-referenced ranges are also possible
(e.g., a thickness of greater than or equal to about 0.01 mm and
less than or equal to about 5 mm, a thickness of greater than or
equal to about 0.1 mm and less than or equal to about 2 mm). Other
values of thickness are also possible. The thickness may be
determined according to the standard TAPPI T411.
The mean flow pore size may be selected as desired. For instance,
in some embodiments, the support layer may have a mean flow pore
size of greater than or equal to about 1 micron, greater than or
equal to about 5 microns, greater than or equal to about 10
microns, greater than or equal to about 30 microns, greater than or
equal to about 50 microns, greater than or equal to about 100
microns, greater than or equal to about 120 microns, greater than
or equal to about 150 microns, greater than or equal to about 300
microns, greater than or equal to about 500 microns, greater than
or equal to about 1000 microns, greater than or equal to about 2000
microns, greater than or equal to about 3000 microns, or greater
than or equal to about 4000 microns. In some instances, the support
layer may have an average mean flow pore size of less than or equal
to about 5000 microns, less than or equal to about 4000 microns,
less than or equal to about 3000 microns, less than or equal to
about 2000 microns, less than or equal to about 1000 microns, less
than or equal to about 500 microns, less than or equal to about 300
microns, less than or equal to about 150 microns, less than or
equal to about 120 microns, less than or equal to about 100
microns, less than or equal to about 50 microns, less than or equal
to about 30 microns, less than or equal to about 10 microns, or
less than or equal to about 5 microns. Combinations of the
above-referenced ranges are also possible (e.g., greater than or
equal to about 30 microns and less than or equal to about 150
microns, greater than or equal to about 50 microns and less than or
equal to about 120 microns). Other values of mean flow pore size
are also possible. The mean flow pore size may be determined
according to the standard ASTM E1294 (2008) (M.F.P.).
In some embodiments, the support layer may have a larger mean flow
pore size than that of the fiber web.
The filter media described herein (which may optionally include two
or more layers) may have certain structural characteristics such as
overall basis weight. In some embodiments, the filter media may
have an overall basis weight of greater than or equal to about 2
g/m.sup.2, greater than or equal to about 5 g/m.sup.2, greater than
or equal to about 10 g/m.sup.2, greater than or equal to about 20
g/m.sup.2, greater than or equal to about 30 g/m.sup.2, greater
than or equal to about 40 g/m.sup.2, greater than or equal to about
60 g/m.sup.2, greater than or equal to about 100 g/m.sup.2, greater
than or equal to about 150 g/m.sup.2, greater than or equal to
about 200 g/m.sup.2, greater than or equal to about 250 g/m.sup.2,
greater than or equal to about 350 g/m.sup.2, greater than or equal
to about 500 g/m.sup.2, greater than or equal to about 800
g/m.sup.2, greater than or equal to about 1000 g/m.sup.2, greater
than or equal to about 2000 g/m.sup.2, greater than or equal to
about 2500 g/m.sup.2. In some instances, the filter media may have
an overall basis weight of less than or equal to about 2800
g/m.sup.2, less than or equal to about 2500 g/m.sup.2, less than or
equal to about 2000 g/m.sup.2, less than or equal to about 1000
g/m.sup.2, less than or equal to about 800 g/m.sup.2, less than or
equal to about 500 g/m.sup.2, less than or equal to about 300
g/m.sup.2, less than or equal to about 200 g/m.sup.2, or less than
or equal to about 100 g/m.sup.2, less than or equal to about 60
g/m.sup.2, less than or equal to about 40 g/m.sup.2, less than or
equal to about 20 g/m.sup.2, less than or equal to about 10
g/m.sup.2, or less than or equal to about 5 g/m.sup.2. Combinations
of the above-referenced ranges are also possible (e.g., greater
than or equal to about 40 g/m.sup.2 and less than or equal to about
2800 g/m.sup.2, greater than or equal to about 60 g/m.sup.2 and
less than or equal to about 800 g/m.sup.2). Other values of overall
basis weight are also possible. The overall basis weight may be
determined according to the standard ASTM D-846.
The overall air permeability of the filter media described herein
can vary. In some embodiments, the overall air permeability of the
filter media may be, for example, greater than or equal to about
0.7 L/m.sup.2s, greater than or equal to about 1 L/m.sup.2s,
greater than or equal to about 5 L/m.sup.2s, greater than or equal
to about 10 L/m.sup.2s, greater than or equal to about 15
L/m.sup.2s, greater than or equal to about 25 L/m.sup.2s, greater
than or equal to about 50 L/m.sup.2s, greater than or equal to
about 100 L/m.sup.2s, greater than or equal to about 150
L/m.sup.2s, greater than or equal to about 200 L/m.sup.2s, greater
than or equal to about 250 L/m.sup.2s, greater than or equal to
about 300 L/m.sup.2s, greater than or equal to about 500
L/m.sup.2s, greater than or equal to about 700 L/m.sup.2s, greater
than or equal to about 1000 L/m.sup.2s, or greater than or equal to
about 1200 L/m.sup.2s. In some instances, the overall air
permeability of the filter media may be, for example, less than or
equal to about 1500 L/m.sup.2s, less than or equal to about 1200
L/m.sup.2s, less than or equal to about 1000 L/m.sup.2s, less than
or equal to about 700 L/m.sup.2s, less than or equal to about 500
L/m.sup.2s, less than or equal to about 300 L/m.sup.2s, less than
or equal to about 250 L/m.sup.2s, less than or equal to about 200
L/m.sup.2s, less than or equal to about 150 L/m.sup.2s, less than
or equal to about 100 L/m.sup.2s, less than or equal to about 50
L/m.sup.2s, less than or equal to about 25 L/m.sup.2s, less than or
equal to about 20 L/m.sup.2s, less than or equal to about 15
L/m.sup.2s, less than or equal to about 10 L/m.sup.2s, less than or
equal to about 5 L/m.sup.2s, or less than or equal to about 1
L/m.sup.2s. Combinations of the above-referenced ranges are also
possible (greater than or equal to about 0.7 L/m.sup.2s and less
than or equal to about 1500 L/m.sup.2s, greater than or equal to
about 15 L/m.sup.2s and less than or equal to about 700
L/m.sup.2s). Other ranges of overall air permeability are also
possible. As determined herein, the overall air permeability is
measured according to standard TAPPI T251 (wherein the flow is
10,000 L/m.sup.2/s on 20 cm.sup.2 area). The permeability of a
filter media is an inverse function of flow resistance and can be
measured with a Frazier Permeability Tester. The Frazier
Permeability Tester measures the volume of air per unit of time
that passes through a unit area of media at a fixed differential
pressure across the media.
The overall thickness of the filter media may be selected as
desired. For instance, in some embodiments, the filter media may
have an overall thickness of greater than or equal to about 0.1 mm,
greater than or equal to about 0.2 mm, greater than or equal to
about 0.3 mm, greater than or equal to about 0.4 mm, greater than
or equal to about 0.5 mm, greater than or equal to about 1.0 mm,
greater than or equal to about 1.5 mm, greater than or equal to
about 2 mm, greater than or equal to about 5 mm, greater than or
equal to about 10 mm, greater than or equal to about 20 mm, greater
than or equal to about 30 mm, or greater than or equal to about 40
mm. In some instances, the filter media may have an overall
thickness of less than or equal to about 50 mm, less than or equal
to about 40 mm, less than or equal to about 30 mm, less than or
equal to about 20 mm, less than or equal to about 10 mm, less than
or equal to about 5 mm, less than or equal to about 2.0 mm, less
than or equal to about 1.2 mm, less than or equal to about 0.5 mm,
less than or equal to about 0.4 mm, less than or equal to about 0.3
mm, or less than or equal to about 0.2 mm. Combinations of the
above-referenced ranges are also possible (e.g., a thickness of
greater than or equal to about 0.01 mm and less than or equal to
about 50 mm, a thickness of greater than or equal to about 0.1 mm
and less than or equal to about 30 mm). Other values of overall
thickness are also possible. The thickness may be determined
according to the standard TAPPI T411.
The filter media, filter element, fiber web and/or support layer
may also include other components, such as a binder resin, surface
treatments, and/or additives. In general, any suitable binder resin
may be used to achieve the desired properties. For example, the
binder resin may be polymeric, water-based, or solvent-based. In
certain embodiments, the binder resin may also include
additives.
In some embodiments, the fiber web and/or the support layer of a
filter media described herein include a binder resin. Typically, a
binder resin or any additional components, if present, are present
in limited amounts. In some embodiments, the fiber web and/or the
support layer may include wet and/or dry strength binder resins
that include, for example, natural polymers (starches, gums),
cellulose derivatives, such as carboxymethyl cellulose,
methylcellulose, hemicelluloses, synthetic polymers such as
phenolics, latexes, polyamides, polyacrylamides, urea-formaldehyde,
melamine-formaldehyde, polyamides), surfactants, coupling agents,
crosslinking agents, and/or conductive additives, amongst others.
In some embodiments, the binder resin may comprise a thermoplastic
(e.g., acrylic, polyvinylacetate, polyester, polyamide), a
thermoset (e.g., epoxy, phenolic resin), or a combination thereof.
In some cases, a binder resin includes one or more of a vinyl
acetate resin, an epoxy resin, a polyester resin, a copolyester
resin, a polyvinyl alcohol resin, an acrylic resin such as a
styrene acrylic resin, and a phenolic resin. Other binder resins
are also possible.
The binder resin is generally not in fiber form and is to be
distinguished from binder fiber (e.g., multi-component fiber)
described above. In general, the binder resin may have any suitable
composition.
The amount of binder resin in the fiber web and/or support layer
may vary. For instance, in some embodiments, the weight percentage
of binder resin in the fiber web may be greater than or equal to
about 0 wt %, greater than or equal to about 2 wt %, greater than
or equal to about 5 wt %, greater than or equal to about 10 wt %,
or greater than or equal to about 15 wt %. In some cases, the
weight percentage of binder resin in the fiber web may be less than
or equal to about 20 wt %, less than or equal to about 15 wt %,
less than or equal to about 10 wt %, less than or equal to about 5
wt %, or less than or equal to about 2 wt %. Combinations of the
above-referenced ranges are also possible (e.g., a weight
percentage of binder resin of greater than or equal to about 0 wt %
and less than or equal to about 20 wt %, a weight percentage of
binder resin of greater than or equal to about 2 wt % and less than
or equal to about 15 wt %). Other ranges are also possible.
The binder resin may be added to the fibers in any suitable manner
including, for example, in the wet state. In some embodiments, the
binder resin coats the fibers and is used to adhere fibers to each
other to facilitate adhesion between the fibers. Any suitable
method and equipment may be used to coat the fibers, and are
described in the context of coating methods above.
In some embodiments, a binder resin may be added to the fiber web
and/or one or more additional layers by a solvent saturation
process. In certain embodiments, a polymeric material can be
impregnated into filter medium either during or after the filter
medium is being manufactured on a papermaking machine. For example,
after the fiber web is formed, it can be impregnated with a
polymeric material by using a reverse roll applicator following the
just-mentioned method and/or by using a dip and squeeze method
(e.g., by dipping a dried filter media into a polymer emulsion or
solution and then squeezing out the excess polymer by using a nip).
A polymeric material can also be applied to the fiber web and/or
one or more additional layers by other methods known in the art,
such as spraying or foaming. p Fiber webs and/or one or more
additional layers for incorporation into a filter media, as
described herein, may be produced using any suitable processes,
such as using a wet laid process (e.g., a process involving a
pressure former, a rotoformer, a fourdrinier, a hybrid former,
inclined wire, or a twin wire process) or a non-wet laid process
(e.g., a dry laid process, an air laid process, a meltblown
process). In general, a wet laid process involves mixing together
of fibers of one or more type to provide a fiber slurry. The slurry
may be, for example, an aqueous-based slurry. In certain
embodiments, the various fibers are optionally stored separately,
or in combination, in various holding tanks prior to being mixed
together (e.g., to achieve a greater degree of uniformity in the
mixture).
For instance, a first fiber may be mixed and pulped together in one
container and a second fiber may be mixed and pulped in a separate
container. The first fibers and the second fibers may subsequently
be combined together into a single fibrous mixture. Appropriate
fibers may be processed through a pulper before and/or after being
mixed together. In some embodiments, combinations of fibers are
processed through a pulper and/or a holding tank prior to being
mixed together. It can be appreciated that other components may
also be introduced into the mixture.
Any suitable method for creating a fiber slurry may be used. In
some embodiments, further additives are added to the slurry to
facilitate processing. The temperature may also be adjusted to a
suitable range, for example, between 33.degree. F. and 100.degree.
F. (e.g., between 50.degree. F. and 85.degree. F.). In some cases,
the temperature of the slurry is maintained. In some instances, the
temperature is not actively adjusted.
In some embodiments, the wet laid process uses similar equipment as
in a conventional papermaking process, for example, a hydropulper,
a former or a headbox, a dryer, and an optional converter. A layer
can also be made with a laboratory handsheet mold in some
instances. As discussed above, the slurry may be prepared in one or
more pulpers. After appropriately mixing the slurry in a pulper,
the slurry may be pumped into a headbox where the slurry may or may
not be combined with other slurries. Other additives may or may not
be added. The slurry may also be diluted with additional water such
that the final concentration of fiber is in a suitable range, such
as for example, between about 0.01% to 0.5% by weight, or between
about 0.1% and 0.5% by weight.
In some cases, the pH of the fiber slurry may be adjusted as
desired. For instance, fibers of the slurry may be dispersed under
generally neutral conditions.
Before the slurry is sent to a headbox, the slurry may optionally
be passed through centrifugal cleaners and/or pressure screens for
removing unfiberized material. The slurry may or may not be passed
through additional equipment such as refiners or deflakers to
further enhance the dispersion or